We're all baseball fans here, so I feel safe in assuming that we all love stud rookies. They give us the warm fuzzies.
On the flip side, I also feel safe in assuming that we all fear what could happen to our favorite rookies. That dreaded phrase: "sophomore slump."
[Ominous piano keys. Thunder. Wolves howling. Floorboards creaking.]
Yes, the sophomore slump is a terribly scary thing, and we have enough evidence that says it's a very real thing. It's by no means unheard of for guys to go from being stud rookies one minute to being shell-shocked sophomores the next.
Want to know how you might be able to see sophomore slumps coming? You really want to know?
Then follow me this way, please.
For Hitters
I went digging around on Baseball-Reference.com and drew up a list of the best rookie seasons (by WAR's reckoning) since 1993, the first of two expansion years in Major League Baseball in the 1990s. I then went looking for hitters who: a) got their share of playing time the next season and b) slumped horribly at the plate.
I found a couple of trends that serve as warning signs of an incoming sophomore slump, starting with...
Beware BABIP Regressions
There are few stats more useful than BABIP, which stands for Batting Average on Balls in Play if you're just now rejoining us following your vacation to Mars.
It's just what it sounds like, and many, many great seasons over the years have been enjoyed thanks to inflated BABIPs. That includes rookie seasons.
The trouble is that inflated BABIPs are extremely hard to maintain. The higher a player goes above his career norm or the league average, the more likely he is to come back to earth the following season.
Rookies don't come into the league with career norm BABIPs, so the league average will have to do for this discussion. Consider the following seven rookies and how their BABIPs compared to the league average.
| Player | Rookie Year | BABIP | League Avg. BABIP* |
| Ichiro Suzuki | 2001 | .369 | .296 |
| Marlon Byrd | 2003 | .360 | .294 |
| Scott Podsednik | 2003 | .361 | .294 |
| Hunter Pence | 2007 | .377 | .303 |
| Jason Heyward | 2010 | .335 | .297 |
| Austin Jackson | 2010 | .396 | .297 |
| Dustin Ackley | 2011 | .339 | .295 |
*Courtesy of FanGraphs.
You can see that the league-average BABIP is going to be right around .300 in a given year. The best players are going to be able to maintain BABIPs over the league average, especially if they have speed to burn. But there's always a good chance that high BABIPs like the ones seen here won't stay high for long.
One reason for that is plain luck. It obviously takes a good hitter to post a high BABIP, but luck can make a good hitter a great hitter. Likewise, luck can go away and take that same hitter from great down to good, or worse.
As for when a player's luck is going to catch up with him, the likely answer is sooner rather than later.
Here's a look at the BABIPs the above hitters posted in the first month of their sophomore seasons, as well as where their BABIPs ended up when all was said and done.
| Player | 1st Month BABIP | Final BABIP |
| Ichiro Suzuki | .344 | .344 |
| Marlon Byrd | .279 | .270 |
| Scott Podsednik | .342 | .275 |
| Hunter Pence | .312 | .301 |
| Jason Heyward | .260 | .260 |
| Austin Jackson | .265 | .340 |
| Dustin Ackley | .288 | .265 |
Here, the only guy who didn't immediately suffer a BABIP regression was Scott Podsednik in 2004. The others were not so lucky, as they all posted BABIPs lower than their final BABIPs from their rookie seasons.
It was bound to happen, and it's something to keep an eye on whenever there's a player looking to repeat a high rookie BABIP in his sophomore season. Odds are luck is going to catch up to him.
That means you, Mike Trout. His .383 BABIP in 2012 was one of the highest in the majors, not to mention close to 90 points higher than the league average.
Like Ichiro earlier in his career, Trout should be able to maintain a higher BABIP than most thanks to his speed, as he'll be able to leg out his fair share of infield singles.
The hits beyond the infield, however, are unlikely to be as frequent for Trout as they were in 2012, and we're likely to be aware that something's up by the end of the month.
Beware Half-to-Half ISO Regressions
All hitters are at the mercy of good and bad luck when they put the ball in play, but guys who can hit the ball hard generally are going to hit the ball hard. As the kids these days might say, power hitters gonna hit for power.
Rookies, however, are unproven as power hitters. They can easily go from crushing the ball one minute to not crushing the ball the next minute. The trend can start in their rookie seasons and continue right on into their sophomore seasons.
Isolated Power (ISO for short) is a stat that can help us out here. It measures how good a hitter is at hitting for extra bases, which essentially makes it a slugging percentage that doesn't take singles into consideration.
Here's a look at a few rookies who were collecting many extra-base hits early, but fewer extra-base hits late.
| Player | Rookie Year | Rookie ISO | 1st Half ISO | 2nd Half ISO |
| Mike Cameron | 1997 | .174 | .183 | .170 |
| Lew Ford | 2004 | .148 | .160 | .133 |
| Hunter Pence | 2007 | .217 | .247 | .171 |
| Jason Heyward | 2010 | .179 | .204 | .155 |
| Dustin Ackley | 2011 | .144 | .232 | .121 |
We're admittedly talking about a pretty small sample size for Dustin Ackley's first-half showing in 2011, as he didn't get the call to the majors until midway through June. He happened to collect quite a few extra-base hits right away.
But after the break, not so much. The same goes for the other four guys, who hit for less power down the stretch than they had been hitting for before.
Now let's take a look at how these players fared in the first month of their sophomore seasons, and how they ended up after that.
| Player | 1st Month ISO | Final ISO |
| Mike Cameron | .061 | .126 |
| Lew Ford | .115 | .113 |
| Hunter Pence | .120 | .197 |
| Jason Heyward | .263 | .162 |
| Dustin Ackley | .093 | .102 |
The only guy who didn't pick up right where he left off was Jason Heyward in 2011, as he raked to the tune of a .263 ISO and seven homers in April. His power numbers did fall off eventually, but that had much to do with a shoulder issue that he developed in early May.
Heyward can be excused for the lesser power numbers he posted as a sophomore. The other guys, however, warned that they weren't going to hit for as much power as they did early on in their rookie seasons, and they were true to form in their sophomore seasons.
One guy who stands out as a good case study for 2013 is Todd Frazier. He posted a .225 ISO as a rookie last year, but his ISO fell from .278 in the first half to .186 in the second half. That's quite the drop, and he may not be able to get back to where he was.
Other Nasty Things to Watch Out For
Some sophomore slump warning signs aren't going to materialize until the first month of the sophomore season in question. Two key categories to keep an eye on are strikeouts and walks. A sophomore slump is very likely to involve more of the former and less of the latter.
Case in point, take a look at some strikeout fluctuations among these guys.
| Player | Rookie K% | 1st Month Soph. K% | Final Soph. K% |
| Chris Singleton | 8.5 | 12.6 | 15.1 |
| Ichiro Suzuki | 7.2 | 8.0 | 8.5 |
| Lew Ford | 11.4 | 17.4 | 14.4 |
| Austin Jackson | 25.2 | 30.5 | 27.1 |
This is a small sample size, so it's hardly guaranteed that a spike in strikeouts in April is going to lead to an overall spike in strikeouts. But we're talking early warning signs here, not prophecies. This is something that certainly can happen, even to hitters as good at avoiding strikeouts as Ichiro was back in the day.
As for walks, you obviously want to keep an eye out if a hitter starts taking fewer walks in April of his sophomore season than he had been in his rookie year. These guys can demonstrate.
| Player | Rookie BB% | 1st Month Soph. BB% | Final Soph. BB% |
| Mike Cameron | 12.3 | 10.7 | 8.4 |
| Marlon Byrd | 8.0 | 7.1 | 5.8 |
| Lew Ford | 10.2 | 4.7 | 7.6 |
| Jason Heyward | 14.6 | 12.4 | 11.4 |
| Dustin Ackley | 10.6 | 7.6 | 8.8 |
Again, it's not a given that an immediate decrease in walks is going to lead to an overall decrease in walks, but it can happen.
Why exactly can early struggles in the strikeouts and walks departments lead to season-long struggles?
Well, BABIP has to do with luck and ISO has to do with power, but strikeouts and walks have to do with approach. That's something that the majority of new major leaguers are still going to be working on, and that's something that seasoned major league pitchers are going to know how to exploit.
Pitchers are going to have a clearer picture of a young hitter's weaknesses in his sophomore season than they did in his rookie season. By making adjustments and attacking those weaknesses, they put pressure on a young hitter to adjust right back.
Some will be able to do it. Others won't. The ones who won't be able to adjust could reveal themselves very early on in their sophomore seasons.
Now then...How about pitchers?
For Pitchers
To find pitcher sophomore slumps to focus on, I did the same thing I did with hitters: Go on Baseball-Reference.com and dial up a list of the best rookie seasons since 1993 and then see who struggled the next year.
Once again, not many trends tied them all together. But the most important one to keep an eye on should sound familiar.
Beware BABIP Regressions
Yup, the BABIP road goes both ways. Just as you have to be wary of hitters who posted curiously high BABIPs as rookies, you have to be wary of pitchers who posted curiously low BABIPs as rookies.
The reasoning is the same, except upside down. With hitters, what goes up must come down. With pitchers, what goes down must come up.
Behold these six pitchers, and I've included their rookie ERAs for the sake of a future comparison.
| Player | Rookie Year | BABIP | League Avg. BABIP | ERA |
| Rodrigo Lopez | 2002 | .256 | .289 | 3.57 |
| Brandon Webb | 2003 | .264 | .291 | 2.84 |
| Zack Greinke | 2004 | .267 | .293 | 3.97 |
| Joe Blanton | 2005 | .248 | .292 | 3.53 |
| Jered Weaver | 2006 | .237 | .298 | 2.56 |
| Armando Galarraga | 2008 | .236 | .296 | 3.73 |
We already know that the league-average BABIP is going to be right around .300 in a given year. And just as there aren't that many hitters in the league who can consistently blow away the league-average BABIP from year to year, there aren't that many pitchers who can live well below it from year to year.
Pitchers who live well below the league-average BABIP as rookies should therefore be regarded with suspicion. They're probably not going to be able to do it again and, naturally, bad luck is likely to catch up to them right away.
Just look what happened to our six test subjects in their sophomore seasons.
| Player | 1st Month BABIP | Final BABIP | ERA |
| Rodrigo Lopez | .330 | .340 | 5.82 |
| Brandon Webb | .272 | .285 | 3.59 |
| Zack Greinke | .292 | .335 | 5.80 |
| Joe Blanton | .343 | .335 | 4.82 |
| Jered Weaver | .333 | .312 | 3.91 |
| Armando Galarraga | .286 | .298 | 5.64 |
No exceptions here. All six posted BABIPs in April of their sophomore years that were higher than their rookie BABIPs, and all six were unable to stop the bleeding. They all went on to post higher BABIPs, and their ERAs suffered accordingly.
There wasn't a rookie hurler who made a significant number of starts last year and got as lucky as the six guys we just looked at, but keep an eye on Wei-Yin Chen. He got by with a BABIP of .274 last year, close to 20 points below the league average (FanGraphs).
Also, Chen posted an 18.8 strikeout percentage, a whole point below the league average (FanGraphs). It's not like he was keeping that many balls out of play, so odds are he's in for a BABIP regression in 2013.
Beware LOB% Luck
A super-low BABIP isn't the only thing rookie pitchers are going to have a hard time sustaining in their sophomore years. They're also going to have a hard time sustaining a high LOB%.
That stands for Left on Base Percentage. It's just what it sounds like, and it's another stat that generally involves pitchers staying right around the league average. In FanGraphs' words:
Most pitchers have LOB%s around league average (which is approximately 70-72%, depending upon the season), and pitchers that deviate from that average tend to see their numbers regress towards average in the future.
Naturally, the higher above the league average a pitcher goes, the more likely it is that his LOB% is going to regress the next year. There have been a handful of rookies in recent memory who can vouch, such as these guys.
| Player | Rookie Year | LOB% | League LOB%* |
| Rolando Arrojo | 1998 | 78.1 | 70.8 |
| Dontrelle Willis | 2003 | 77.6 | 71.2 |
| Zack Greinke | 2004 | 80.4 | 71.4 |
| Jered Weaver | 2006 | 86.2 | 70.9 |
| Vance Worley | 2011 | 78.2 | 72.5 |
*Courtesy of FanGraphs.
You can see from this little selection that it's indeed true that the league-average LOB% is generally in the low 70s. The five pitchers we have here all posted a LOB% near or over 80 in their rookie seasons.
Good stuff at the time, to be sure, but also an ill omen. The smart money was on them allowing more baserunners to score in their sophomore seasons.
Sure enough, here's how they ended up doing.
| Player | Final LOB% | League LOB% |
| Rolando Arrojo | 74.6 | 70.3 |
| Dontrelle Willis | 71.7 | 71.4 |
| Zack Greinke | 65.2 | 71.7 |
| Jered Weaver | 73.6 | 70.7 |
| Vance Worley | 72.6 | 72.5 |
Dontrelle Willis and Vance Worley both regressed to about the league average in their sophomore seasons. Rolando Arrojo and Jered Weaver came reasonably close to regressing that far. Poor Zack Greinke just couldn't catch a break.
Like with BABIP, this is a "bound to happen" scenario. Not every pitcher who posts a high LOB% one year is going to let everyone come around to score the next, and some pitchers get pretty good at avoiding that fate. But it's always a good bet that any pitcher with a high LOB% one year is going to have luck catch up to him the next, and rookies are no exception.
Among the heavy-workload rookies in 2012, Lance Lynn and Jarrod Parker went above the league-average LOB% the most (FanGraphs). The guys who really bear watching, however, are Hisashi Iwakuma and Miguel Gonzalez, who both posted a LOB% of 83.0 last year. They're very likely to come back down to earth in 2013.
Other Nasty Things to Watch Out For
It didn't apply to that many of the pitchers I looked at, but another "bound to happen" scenario involving rookie pitchers pertains to home runs.
Keep an eye out for rookie pitchers who are able to post a low HR/FB (Home Run to Fly Ball) rate despite a low ground-ball percentage. Three guys who come to mind are Rodrigo Lopez, Dontrelle Willis and Vance Worley.
Lopez posted a 10.1 HR/FB rate in 2002 despite having just a 40.2 ground-ball rate (FanGraphs). Though it wasn't exactly low, his HR/FB rate probably should have been higher. The next season saw him only marginally increase his ground-ball and strikeout rates, so it's no surprise his HR/FB increased to 13.7 percent.
Willis posted a 7.9 HR/FB in 2003 despite a mere 40.7 ground-ball rate (FanGraphs). With so few balls ending up on the ground, he should have posted a higher HR/FB. He did just that in 2004, as his HR/FB rate took a climb up to 9.0.
Worley had a 7.2 HR/FB rate in 2011 despite having a ground-ball percentage under 40 (FanGraphs). He did induce more ground balls in 2012, but his HR/FB rate regressed to 9.8 percent anyway.
You get the idea. It's not a given that a pitcher's HR/FB rate is going to increase after being low one year, but it's very likely to increase if the pitcher in question is not a ground-ball hoarder.
Beyond this trend, do you remember how we looked at hitters who teased in the latter half of their rookie seasons that they would be striking out more in their sophomore seasons?
Same thing goes for pitchers, except the other way around. You have to keep an eye out for rookie hurlers whose strikeout totals took a dive as the year went along.
Take Willis and Jered Weaver, for example.
| Pitcher | Rookie K% | 1st Half K% | 2nd Half K% | Soph. 1st Month K% | Final K% |
| Willis | 21.3 | 24.0 | 18.6 | 15.1 | 16.4 |
| Weaver | 21.4 | 24.0 | 20.3 | 17.7 | 16.6 |
The symmetry here is uncanny, but it's not very surprising. Willis and Weaver took the league by storm in part thanks to their deceptive deliveries. It follows that hitters would do their homework and come up with a good idea of how to approach them, and that their strikeouts would tumble accordingly.
That's what happened. Both Willis and Weaver saw their punchouts decline in the latter half of their rookie campaigns, and the trend continued straight on into their sophomore seasons. That helps explain their LOB% regressions, which helps explain their sophomore slumps.
It's also possible for a rookie pitcher to tease a walk regression. These were harder to come by in my search, but one guy who stuck out like a sore thumb was Brandon Webb. Observe:
| Rookie BB% | 1st Half BB% | 2nd Half BB% | Soph. 1st Month BB% | Final BB% |
| 9.1 | 6.7 | 11.5 | 14.1 | 12.8 |
Sort of like how Willis and Weaver experienced significant drop-offs in strikeouts in the second half of their rookie seasons, Webb experienced a significant spike in walks in the second half of his rookie campaign. The trend continued into the next season.
It's not surprising in the slightest that Webb's increased walk rate came paired with a greatly decreased O-Swing%, or the percentage of pitches he got hitters to swing at outside of the strike zone (FanGraphs). He was able to feast on hitters who were willing to expand the zone in his rookie season, but then they adjusted to him.
Such is life when it comes to sophomore slumps. If they're going to happen, they're going to happen because nature is taking its course and/or because the league is catching up and showing a hot-shot youngster what's what.
Note: Stats courtesy of Baseball-Reference.com.
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