Heyward, Pedroia, and Your Annual Warning About Defense

We all know, entering the season, that the WAR leaderboards in the early part of the year reveal less about the players contained within them than those same WAR leaderboards at the end of the year. That knowledge doesn’t stop me, personally, from compulsively looking at the leaderboards just as soon as the season begins. Remember Freddy Galvis? He was tied for the National League lead among shortstops with 0.9 WAR — and “on pace” for a great season at the end of April. A month of replacement-level production has placed him considerably lower among major-league shortstops. What about Devon Travis? At the end of April, his 1.4 WAR was sixth in all of baseball. Unfortunately, an injury slowed him down and he has been unable to add to his impressive April totals.

Now that we have reached the second week of June, the leaderboards begin to look a little more familiar. Mike Trout, Josh Donaldson, and Paul Goldschmidt have continued great runs of production. Bryce Harper has emerged and Jason Kipnis has returned to form after a poor 2014 season. There are still surprises at this point, though. The production of Harper and Kipnis was not expected to reach these levels, Joc Pederson has been far more impressive than anyone could have expected, and Dee Gordon is still slapping and running his way into the top ten. We will see more changes as the season wears on, providing a more accurate depiction of player value as more games are played. However, since we are all looking at the leaderboards now, it might be worthwhile to point out a few anomalies in WAR totals due to the small sample sizes we have with defensive statistics.

This might be old hat for some, but it’s important to keep in mind that defensive statistics are not tremendously reliable after just a few months when trying to determine the talent level of the fielder. In his UZR Primer, Mitchel Lichtman compares the reliability of UZR to OPS.

Most of you are familiar with OPS, on base percentage plus slugging average. That is a very reliable metric even after one season of performance, or around 600 PA. In fact, the year-to-year correlation of OPS for full-time players, somewhat of a proxy for reliability, is almost .7. UZR, in contrast, depending on the position, has a year-to-year correlation of around .5. So a year of OPS data is roughly equivalent to a year and half to two years of UZR.

Our FanGraphs library provides the following caveat:

Beware of sample sizes! If a player only spent 50 innings at a position last season, it’d be a good idea not to draw too many conclusions from their UZR score over that time. Like with any defensive statistic, you should always use three years of UZR data before trying to draw any conclusions on the true talent level of a fielder.

With that in mind, I attempted to find players whose current WAR totals might be weighed down by unusual defensive numbers early in the season compared to what would generally be expected given what we know about a player’s talent level. To find appropriate players to study, I looked at only those players who were qualified hitters from 2012 to 2014, who did not change positions, and who are also qualified this season. These 70 players all accumulated at least 2,500 innings on defense in the previous three years, with some players having significantly more time in the field. While young players and players who have changed positions could have some unusually high or low UZR numbers affecting their WAR, those players do not have the track record to appropriately compare prior numbers.

To get a general determination of how far the 2015 numbers were diverting from the previous three seasons, I took the three-year defensive runs, divided by three to get to one year, and then divided by three again (also called dividing by nine), as we are one-third of the way through this season. I compared that number to the current season’s defensive-runs number. Most players were relatively close to previous years, with 60% of the 70 players within three runs of prior years and 80% of players within five runs. Below are some of the players who appear to have been hurt the most in WAR by lower than typical defensive numbers. For each player, the seasonal average is used for 2012-2014, and Def includes the positional adjustment.

Dustin Pedroia

Dustin Pedroia	DRS	UZR	Def	1/3 Season Def
2012-2014 AVG	14.3	13.0	15.2	5.1
2015	0.0	-1.4	-0.6	-0.6
DIFFERENCE				-5.6

At 31 years old, Pedroia is likely in the decline phase of his career but the odds of him decling from one of the best second baseman in the game to slightly below average seems unlikely. Pedroia won the last two Fielding Bible Awards and three of the last four. He has hit very well this season, with a 133 wRC+ placing his WAR at 1.8 for the season, but it looks like he might be half a win better than his current WAR represents.

Ian Desmond

Ian Desmond	DRS	UZR	Def	1/3 Season Def
2012-2014 AVG	-2.3	3.0	9.7	3.2
2015	-4.0	-5.2	-2.6	-2.6
DIFFERENCE				-5.8

Desmond will never be confused for a defensive star like Pedroia, but his numbers this season are worse than normal for Desmond. DRS and UZR disagree by about five runs per season, and averaging the two would render Desmond a roughly average shortstop, but the numbers this season are much worse. Desmond is having a disappointing season at the plate as well, giving him replacement-level numbers after three straight four-win seasons. Desmond is not playing well this season, but his replacement-level WAR is likely not as bad as it should be.

Jason Heyward

Jason Heyward	DRS	UZR	Def	1/3 Season Def
2012-2014 AVG	22.3	20.0	14.2	4.7
2015	4.0	0.9	-1.4	-1.4
DIFFERENCE				-6.1

Like Pedroia, Heyward has an excellent defensive reputation, winning the Fielding Bible Award for right field in 2012 and again last season. Unlike Pedroia, Heyward has not gotten off to as good a start with the bat, hitting .217/.261/.349 in April. He got better results in May with a wRC+ of 115, but his WAR still sits at 0.3 due to his poor April and defensive numbers that might not represent his talent.

Talent that allows him to do this, that is:

Denard Span

Denard Span	DRS	UZR	Def	1/3 Season Def
2012-2014 AVG	6.7	4.4	6.5	2.2
2015	-4.0	-5.1	-4.5	-4.5
DIFFERENCE				-6.7

Denard Span has generally been an above-average center fielder during his career, although there is a little less confidence regarding Span’s talent level on defense compared to the players above him on this list. Span’s negative numbers last season by themselves would not really mean a whole lot, but taken with this year’s numbers, his age (31), and the fact he had knee surgery in March might mean that his 2015 defensive numbers are closer to reality than we might think. Even with those concerns, it’s unlikely that Span is actually close to 20 runs below average over the course of a full season as his current UZR might make him seem.

Chase Headley

Chase Headley	DRS	UZR	Def	1/3 Season Def
2012-2014 AVG	5.0	11.7	13.9	4.6
2015	-8.0	-6.4	-5.5	-5.5
DIFFERENCE				-10.1

Headley is another player who’s a little bit tough to figure out right now. He has an excellent defensive reputation, but he has also made seven throwing errors on the season, a problem he is working on. Headley is likely to be good going forward, but given his throwing problems, which did not seem to be present previously, it is likely that he has not been as good defensively as in prior years.

Looking at leaderboards can be an enjoyable experience, but, even at this stage of the season, there is a lot of movement remaining before the end of the year. It’s easy to look at a player’s WAR right now, multiply by three, and say they are on pace for an x-win season, but given defensive sample sizes, doing so can misrepresent the likely true-talent levels for players like Pedroia and Heyward.