Explaining the Most Surprising Hot Starts in MLB

In the old days, there was no explaining hot April starts in Major League Baseball.

But these are the new days. We have numbers that explain everything that needs explaining, making it pretty easy to understand what's under the hood of hot April starts.

So that's what we're going to do, while we still have a few days left to go until the end of April. And when I say "we," I mean I'm going to ramble on about a couple guys while you sit there and nod.

I want to talk about six guys in particular: three hitters and three pitchers. The three hitters I want to talk about are Chris Davis, Chris Johnson and Justin Upton. The three pitchers I want to talk about are Clay Buchholz, Paul Maholm and Matt Moore, who occupy the top of the ERA standings.

There are many more hot starts worth talking about. Too many, in fact. If I were to venture to explain every single surprising hot start we've seen so far, the result would be a book-length article that would get boring after, say, 15 minutes.

So we'll keep it at six, and we'll get the ball rolling with the hitters.

 

Chris Davis

Next to guys like Adam Jones, Manny Machado and Matt Wieters, it was easy to overlook Baltimore Orioles slugger Chris Davis heading into the season.

It's not so easy to do that now. Even after cooling down after a torrid start, Davis is still hitting .368/.457/.776 and is currently tied for second in the majors with eight home runs.

The first thing that's easy to notice about Davis' April is his vastly improved approach. Per FanGraphs, he's doubled his walk rate from where it was last year while also cutting his strikeout percentage down from 30.1 to 22.8.

The odd part is that Davis isn't seeing more pitches per plate appearance than he was last year. His P/PA in 2012 was 4.00. So far this year, it's 3.71. 

But that doesn't necessarily mean he's being more aggressive. Here are some key plate-discipline numbers, which come courtesy of Baseball Info Solutions via FanGraphs:

Year	O-Swing%	Z-Swing%	Swing%	Z-Contact%	Contact%	SwStr%
2012	39.8	77.6	54.9	82.5	71.0	15.5
2013	34.3	77.4	52.0	90.6	75.2	12.0

*FanGraphs has definitions for all these terms if you need them.

The things that stand out here are the O-Swing, Swing and SwStr numbers. In general, they show that Davis is taking better hacks, as he's not expanding the strike zone, and he's not whiffing on pitches.

Davis is still attacking pitches inside the zone at roughly the same rate he did last year. The difference is that he's making far more contact when he swings at pitches inside the zone.

And pitches inside the strike zone, obviously, are easier to hit. Given how much contact Davis has made on pitches in the zone, it's no wonder he has a .408 BABIP.

That number is certainly going to come down as the season moves along, but don't be so quick to write off Davis' 30.8 HR/FB rate. This is a guy who maintained a 25.2 HR/FB rate last year, and we know he has loads of power.

Davis is showing off some good habits this year. If he maintains them, he'll be in for a big season.

 

Chris Johnson

Heading into the season, Chris Johnson was just one of the guys who was going to try to fill in for Chipper Jones at third base for the Atlanta Braves.  But guess who's currently leading all of baseball with a .397 batting average?

Like with Davis, Johnson has drastically cut down on his strikeouts. Johnson struck out 25 percent of the time last season, which was about normal for him. So far this year, he's only striking out 16.7 percent of the time.

Unlike Davis, however, Johnson isn't walking more. In fact, he's only drawn two walks all season in 66 plate appearances. Even for him, that's a low rate. Also unlike Davis, Johnson's plate discipline numbers are a mixed bag. 

Year	O-Swing%	Z-Swing%	Swing%	Z-Contact%	Contact%	SwStr%
2012	37.4	66.6	50.6	87.5	76.9	11.9
2013	35.8	72.9	53.3	89.7	77.7	11.7

You can see that Johnson is swinging at more pitches inside the strike zone, which is good. But his Z-Contact rate and overall contact rate have only marginally increased. He's also swinging and missing about as often as he did last year.

It thus feels fluky that Johnson has put as many balls in play as he has. What feels even more fluky is how many of those balls in play have gone for hits, as Johnson's BABIP is an enormous .460.

That's the highest BABIP in baseball, and there's no way it's going to last. Even if Johnson is able to keep putting balls in play at the rate he currently is, his BABIP is going to deflate, and he's only going to be a decent average/low on-base guy.

Not that the Braves won't take that, mind you. They could ask for worse from Chipper's replacement.

 

Justin Upton

I hesitated to slap the "surprise" label on Justin Upton. Heading into the season, everyone knew beyond a shadow of a doubt that he was as talented as they come.

But after the year he had in 2012, yeah, I'd say that a .316/.402/.797 batting line with a league-best 11 homers counts as a surprise. Upton is totally destroying expectations.

Sticking with the pattern I've developed here, the answer is yes: Upton is being more patient in 2013. After seeing under 3.80 pitches per plate appearance in 2011 and 2012, he's seeing 4.13 pitches per plate appearance this year. The biggest change is that he's not chasing the first pitch nearly as often.

Beyond that, there's actually not much about Upton's plate discipline data that really sticks out. There are some subtle differences here and there, but he generally hasn't changed much from last season.

What's really changed is Upton's ability to hit whatever he's offered. We can tell that by looking at some Pitch Type Linear Weights, specifically the weighted varieties that show how many runs above average a hitter has generated against specific pitches on a "per-100 pitch" basis.

Here's how Upton's 2013 production against various pitches compares to his previous career norms:

Span	wFB/C	wSL/C	wCT/C	wCB/C	wCH/C
2007-2012	1.24	-0.62	1.25	0.51	0.78
2013	3.83	0.91	3.83	6.63	5.61

The obvious caveat here is that these are small sample size numbers—they will be leveling out as the season goes along.

Nonetheless, these numbers go to show just how locked in Upton has been. He was doing fine against hard stuff before, but now, he's handling sliders, curveballs and changeups as well. Take those pitches away from pitchers and they don't have much left.

These numbers are also testaments to just how hard Upton is hitting everything he makes contact with. So is his 37.9 HR/FB rate, which is currently tops in the majors.

That number will be coming down, but not too much. After all, it's hard to ramble on about HR/FB flukiness when things like this are happening:

 

Clay Buchholz

We saw Clay Buchholz have a huge season in 2010 when he posted a 2.33 ERA, but it always felt fluky. A guy with a 6.2 K/9 and a 3.5 BB/9 probably should have done worse, and stats like FIP and xFIP suggested that, yeah, he should have done worse.

But this year, what Buchholz is doing looks and feels legit. He has a 1.19 ERA, and both his FIP and xFIP are in the 2.00s. That's a very good place for any pitcher to be.

The biggest change for Buchholz this year has been an increase in strikeouts. He's punched out 27.1 percent of the hitters he's faced, which is pretty high above his career rate of 17.9 percent. He won't be punching hitters out at that rate all season, especially given how he's not doing it with whiffs. Buchholz's 7.9 swinging-strike percentage is below his career mark of 9.1 percent.

Instead, what Buchholz is doing is a better job of pounding the strike zone. Baseball Info Solutions has Buchholz's Zone% at 46.5. PITCHf/x has it at 50.3 percent. Either way, he's ahead of where he was in each of the last two seasons, and it has much to do with how he's throwing all his pitches for strikes.

Here are some called-strike percentages from BrooksBaseball.net:

Span	Four-Seam	Sinker	Cutter	Curveball	Changeup
Career	21.93	18.34	11.23	22.83	12.84
2013	27.50	22.41	13.91	33.73	13.51

This is how you pound the zone. When you do it, you do it with EVERYTHING.

When he's got it all working, every single one of Buchholz's pitches is impressive. But this year, the one that's really stood out is his cutter. He's throwing it more often, and it's been extremely effective against left-handed batters.

Lefty hitters have only two hits against Buchholz's cutter this season, both of them singles. That helps explain the .474 OPS lefty hitters have against him, which looks mighty good compared to his career mark of .718.

Buchholz has always had ace potential. He's realizing it this year even more than he was in 2010.

 

Paul Maholm

Paul Maholm did precisely what the Braves got him for last season, posting a 3.54 ERA in 11 starts after he was acquired in a trade from the Chicago Cubs.

Even while that was going on, however, I doubt the Braves anticipated Maholm leading the league in ERA this April. That's where he is through four starts at 1.03.

Like with Buchholz, a greatly improved strikeout rate stands out when looking at Maholm's stats. He's a guy who has generally struck out around 15 percent of the hitter he's faced. This year, he's struck out 24.3 percent of the hitters he's faced while maintaining a respectable walk rate.

Unlike with Buchholz, however, Maholm is doing it with whiffs. He's getting more swinging strikes than ever before, which is kinda surprising seeing as how his fastball sits in the high 80s.

The main reason for this new trend? That would be Maholm's off-speed stuff, which has been stupendous.

Remember those Pitch Type Linear Weights we looked at? They work for pitchers too, and in Maholm's case, they show that his curveball and changeup have been two of the best off-speed pitches in baseball.

Presently, Maholm owns a 3.61 wCB/C. That's good for fourth in the league among qualified starters. Even better, Maholm owns a 5.81 wCH/C. That's good for third in the league.

It's not a huge shock that Maholm's changeup is so effective, as it was his best pitch last year. It's his curveball that's been a real surprise, as it's traditionally been a hit-or-miss pitch for him.

I should be saying curveballs. Maholm is throwing more than one this year, as he's added a super-slow curve to his arsenal. Ben Lindbergh of Baseball Prospectus noticed it a couple weeks ago, and BrooksBaseball.net is being kind enough to track it for us.

So far, Maholm has only allowed one hit on his slow curve, which averages about 63 MPH. That's a telling sign that it's a good one. If you want somebody else's testimony that it's a good one, you can ask Chase Utley.

 

Matt Moore

Heading into 2012, Matt Moore was the No. 2 prospect in baseball in Baseball America's eyes. He was ahead of Mike Trout, for cryin' out loud.

Now we know why. After a rocky rookie season, Moore has the best ERA in the American League at 1.04. The more he pitches, the more it becomes apparent what the fuss was about.

But Moore's April hasn't been perfect. He still has issues to work out with his control, as he's actually walking batters at a more frequent rate than he was in 2012. His walk percentage has risen from 10.7 to 13.9.

Not surprisingly, both Baseball Info Solutions and PITCHf/x agree that Moore is throwing fewer pitches in the strike zone. He's also not getting hitters to expand the zone as much, and he's not getting as many swinging-strikes as he did last year.

So...what the heck?

Frankly, Moore's Zone% issues do worry me, but the swinging-strike thing doesn't worry me so much. Here's a look at the whiff rates of Moore's key pitches this year compared to the rest of his career, courtesy of BrooksBaseball.net:

Span	Four-Seam	Sinker	Curveball	Changeup
Career	11.29	8.58	13.89	19.39
2013	6.55	11.76	15.84	20.29

To clarify, there is a difference between swinging-strike rate (SwStr%) and whiff rate. According to FanGraphs, the first is swinging strikes per pitch. The second is swinging strikes per swing.

All the same, what you see here is that hitters aren't missing Moore's four-seamer, but that they are swinging through his other pitches. That's by no means a distressing trend, especially when it comes to his curve and changeup. Those pitches are supposed to be whiffed at.

Another non-distressing trend is Moore's 47.4 ground-ball percentage, a 10-point increase from last year. That helps explain his .143 BABIP. It's absurdly low, but any Tampa Bay Rays pitcher who can keep the ball on the ground stands a good chance of being successful given how often they shift their infielders.

That BABIP is going to come up eventually, of course. And when it does, Moore's walk rate must come down in order for him to have any hope of maintaining his hot start. He's getting by mainly on his stuff this season.

But fret not, Rays fans. Great stuff can go a long way, and Moore has terrific stuff.

 

Stats courtesy of FanGraphs, unless otherwise noted.

 

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