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Do the stats say Max Kepler is actually a good centerfielder?

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We’re talking defense, baby

Minnesota Twins v Texas Rangers Photo by Tom Pennington/Getty Images

Fans of the Minnesota Twins have been treated to some excellent fielders in center throughout the course of the team’s history. From Puckett to Hunter to Span to Buxton, centerfield has consistently been the home of some of the franchise’s most outstanding fielders. As our resident platinum-glover Buxton has missed time this year, how has Max Kepler lived up to the fielding reputation of the team while filling in out in center?

The eye-test is obviously what most fans use in considering whether a player is a good fielder or not. Kepler, in the eyes of the fans, has been pretty good out in center, while not as spectacular as Buxton has been. What do the defensive statistics of 2019 have to say about this assessment?

Before I bombard you with some alphabet soup, let’s run through some of the metrics that you’ll find in the chart below. Innings will be first up in the chart, to give you an idea of the sample size we’ll have to deal with. Then, from left to right, will be an assortment of statistics ranging from simplest to most involved.

Fielding Percentage- Fielding Percentage is the most understood defensive statistic by fans. It simply measures how many plays are made (not an error) against how many total chances the fielder had.

Revised Zone Rating (RZR)- Revised Zone Rating is the simplest of the three “advanced” metrics in the table. The metric uses a pre-defined “zone”, and then takes into account the total amount of balls hit into this zone, how many plays the fielder made, and how many plays the fielder made out of the zone. To give you some context, Fangraphs defines an average fielder as having about a .835 RZR, and an excellent one having a .940 RZR.

Defense Runs Saved (DRS)- Defensive Runs Saved is designed to measure a player’s total defensive value. While having a pretty involved formula, the metric essentially tells you how many runs a player is worth at his position above the position’s average. This metric is a cumulative stat, so the amount of innings played will factor in (someone with 700 innings played could have a higher DRS than one with 200 innings played, but that doesn’t necessarily suggest he’s a better defender). 5 DRS would be considered above average over a whole season, while 15 DRS would be in Gold Glover territory.

Ultimate Zone Rating Per 150 Games (UZR/150)- Probably the most widely accepted advanced defensive metric, UZR/150 is similar to DRS, but is formulated differently. This metric is scaled per 150 games, so that accumulations over larger sample sizes are corrected (unlike in DRS). Basically, UZR measures the average amount of damage a batted ball would do, how likely it is to be an out, and compares that to the position’s average. Small sample sizes, as with DRS, can cause some unreliability with this statistic.

I compared Kepler to someone we know is spectacular (Buxton) as well as someone who is thought to be about average in centerfield (Cleveland CF Oscar Mercado). Here’s what I found:

Centerfield Defense

PLAYER INNINGS FIELDING PER. RZR DRS UZR/150
PLAYER INNINGS FIELDING PER. RZR DRS UZR/150
Max Kepler 376.0 1.000 0.954 3 19.8
Byron Buxton 686.0 0.991 0.924 10 15.2
Oscar Mercado 441.2 0.992 0.903 2 -2.4

The first thing you’ll notice is that Kepler’s sample size is relatively small, even while none of these three have especially large samples. However, it appears that he has done very well in this sample size. He has not made an error in centerfield this season, giving him the highest fielding percentage of the three. However, fielding percentage is the most simplistic of these metrics, and especially so in the outfield. This is because outfielders are usually only assigned errors on balls they drop (or throw away), and range is not taken into account. Next up, Kepler’s RZR compares favorably to Buxton’s and Mercado’s. However, fielding percentage would heavily influence this in a small sample, as an error made would drop a fielder’s total plays made, thus dropping the RZR.

DRS gives us a better idea of how the three of these players compare to each other. Kepler, even in less innings, has amassed a higher DRS than Mercado, while Buxton has reached a significantly higher level. Buxton does have about twice as many innings played, but his DRS is more than three times higher than Kepler’s. This is what we would expect, but it is still encouraging that Kepler has been better than Mercado in this metric (even in less innings).

UZR/150 may have a sample size issue here, but we’ll go into it anyway. With these samples, we see some rather extreme differences between the players. Buxton’s 15.2 is outstanding (as expected), and Kepler’s is downright off the charts. Mercado’s negative value is probably a little on the low side, but is not too much lower than would be expected for him. We can draw from this that Kepler has been very good in the field in his time in center, but it may be rather dim to take it as proof that Kepler is superior to Buxton in centerfield.

Unfortunately, defensive statistics are still a work in progress, even as deep into the sabermetric age as we are in 2019. Furthermore, there are things that are impossible to quantify, such as the added confidence a pitcher has when a guy with the reputation of Byron Buxton is roaming the outfield behind him. However, by comparing players, we can draw some meaning from the statistics we have.

I’d say that after looking over the metrics, the eye-test assessment most have come to on Kepler in center is rather fair. He falls somewhere between above-average and great in centerfield, and has done an admirable job filling in for the Twins’ excellent normal centerfielder. When Buxton comes back, the Twins will have not one, but two bona fide centerfielders roaming the grassy expanse and chasing down flies (or squirrels).