In Adrian Beltre the Boston Red Sox have acquired a Gold Glove third baseman to replace another Gold Glove third baseman in Mike Lowell. But the Red Sox may have gotten more than they bargained for.

Mike Lowell’s Quick Demise

Until 2009, when hip woes limited both his playing time and his effectiveness, Mike Lowell provided above average, sometimes elite defense at the Fenway hot corner. In 2006, 2007, and 2008, Lowell delivered .987, .961, and .967 fielding percentages and 7.7, 8.0, and 15.6 UZR/150s, respectively.

Aside from demonstrating the remarkable disparity between traditional defensive indicators and newer saber-metric ones, these statistics offer a sharp contrast to Lowell’s 2009 marks of .966 and –14.4. If one considered only Lowell’s fielding percentage, his drastically less effective defense wouldn’t be so transparent.

Given Lowell’s respectable .290 batting average, 17 home-runs, and .811 OPS during the 2009 campaign, replacing him has everything to do with defensive saber-metrics and nothing to do with offensive production.

Enter Adrian Beltre

Adrian Beltre is a career .270 hitter whose 2009 season included sub-par offense, but a MLB best 21.0 UZR/150. Again, Boston’s acquisition of Beltre revolves entirely around defense.

Beltre’s career UZR/150 of 13.9 nearly matches Lowell’s career high of 15.6 in that statistical category.

Putting that another way, on an average day, Adrian Beltre is as good defensively as Mike Lowell is on his best.

Defensively, Beltre effectively replaces Lowell.

Offensively, Beltre seems a severe downgrade.

That is, if one considers only the 2009 numbers. Lowell owns a career batting average of .280, a career on-base percentage of .343, and a career slugging percentage of .468.

Adjusting for the transition from Safeco to Fenway, Beltre should lay down a line closer to .287/.345/.481.

That’s a slight upgrade offensively.

Lowell will always be loved in Boston, but no-cup defense isn’t the only improvement Beltre brings to Fenway.

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