The Red Sox have identified infield defense as a potential area of improvement in 2020, and the next-generation stats tend to agree.
What's surprising is the snapshot provided by the NEXT-next-generation stats, which were unveiled on Wednesday and actually paint a less dire picture, albeit still not exactly an inspiring one.
There's gonna be some math ahead, so bear with me.
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Publicly available defensive metrics remain well behind their offensive counterparts when it comes to reliability. Stats such as ultimate zone rating (UZR) and defensive runs saved (DRS) aren't as laser-precise as the Statcast tracking data used to determine, for instance, launch angle and exit velocity.
That's changing, however. For the past two seasons, Statcast has been able to track the routes outfielders take to fly balls, yielding a wealth of information, from jump to sprint speed to chase angles to distance covered.
The result is outs above average, which is exactly what it sounds like. Last year's leaders included Nationals centerfielder Victor Robles (plus-23), three-time Gold Glover Kevin Kiermaier (plus-17) of the Rays, and Brewers fence-scaler Lorenzo Cain (plus-14), but not, surprisingly, Gold Glover Mookie Betts (plus-7).
On Wednesday, Statcast unveiled infield outs above average, and the 2019 numbers challenge some assumptions we may hold about the Red Sox. (For a primer on the whole system, by the way, MLB.com has you covered.)
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While the numbers don't portray Boston's infield defense as elite, they don't suggest it's terrible, either. The Red Sox ranked 16th in outs above average at plus-3. That pales in comparison to the league-leading Cardinals (plus-42) and Rockies (plus-33), but it's not nearly as bad as Boston's minus-43 defensive runs saved, which trailed only the Mariners in all of baseball.
The differences are particularly stark on the left side of the infield, where shortstop Xander Bogaerts ranked dead last in DRS (minus-21) and Rafael Devers found himself in the bottom 10 at minus-6.
By OAA, however, Bogaerts cost the team just three outs, while Devers actually checked in at plus-7, which better conveys how much he improved after an error-prone April. That put Bogaerts at 23rd out of 35 qualifying shortstops and it actually ranked Devers fourth among third basemen.
So why the difference, and which numbers should we believe? The Statcast leaderboards include more data, factoring in everything from defensive positioning at the point of impact, to the speed and angle of the ball off the bat, to the distance covered by the fielder, to the speed of the runner at the plate. They combine to produce an out probability. Convert a play that's only an out 10 percent of the time, and you'll gain .90 outs to your total. Screw up an in-between grounder deep in the hole, and you might lose half a point.
The numbers suggest that Bogaerts remains a step slow laterally (minus-2 outs to both his left and right), but that he makes the plays he gets to, as evidenced by an 87 percent success rate. Devers, meanwhile, recorded nine extra outs on balls to his left, which trailed only the Gold Glove-winning Nolan Arenado (plus-12) and tracks with the eye test — he's especially effective cutting across the diamond.
The numbers on second baseman Michael Chavis (plus-4) were actually encouraging, and the Red Sox should improve at that spot merely by not entrusting too many innings to Marco Hernandez (minus-2) or any at all to the departed Eduardo Nunez (minus-2).
It's important to note that teams have developed proprietary methods to interpret Statcast defensive data and they don't share their conclusions publicly. That said, the introduction of infield OAA to the mainstream should help refine the way we evaluate infield defense, and we'll see where the Red Sox fall in 2020.
