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What do pitchers do when they know the defense has their back?

Does a good defense encourage pitchers to attack the zone more often?

MLB: Boston Red Sox at Tampa Bay Rays Kim Klement-USA TODAY Sports

There are likely many reasons Chris Sale is having a near-MVP season in 2017. He has always been an electric pitcher, and he seems to have abandoned his quasi-random attempt in 2016 to lower his velocity in order to go deeper into games. He has lowered his home run rate even further, despite league-wide trends in the exact opposite direction. And, despite a few instances in the other direction, he has the support of a much better lineup behind him than he did last season in Chicago. The result is a 14-4 record with a 2.51 ERA, numbers that actually undersell what he has been worth if we use WAR (7.4) and FIP (1.92).

One factor that hasn’t been mentioned as often is that he is pitching in front of the best defense in baseball. (It may not be mentioned that often because he’s striking out nearly every hitter who comes up to the plate, which is a good reason.) Last season, Sale pitched in front of a slightly below-average White Sox defense, one who ranked 16th in MLB in FanGraphs’ Def statistic.

This season, Sale is pitching in front of the top-rated team in the same metric, with an especially strong outfield behind him. With that in mind, it may not be too surprising to see that Sale is allowing a career-high fly ball rate (43.4 percent) and is getting a near-career-high first-pitch strike rate (66.4 percent).

It seems intuitive that a pitcher who has a defense he trusts behind him would feel more confident with the first pitch of each at bat, resulting in a higher percentage of first pitch strikes. It has been the case in our N=1 example of Chris Sale, so does the theory still play on a league-wide basis?

Team defense effects

Team Defense Rank Zone% Rank F-Strike% Rank
Team Defense Rank Zone% Rank F-Strike% Rank
BOS 1 13 2
CIN 2 8 29
KC 3 3 5
LAA 4 26 15
MIA 5 16 26
LAD 6 15 1
CHC 7 24 22
SEA 8 2 8
DET 9 9 24
PHI 10 4 10
CLE 11 7 3
NYY 12 28 9
TEX 13 19 25
SF 14 12 4
COL 15 1 28
WAS 16 6 16
MIN 17 14 14
TB 18 27 19
STL 19 10 21
ARZ 20 25 18
ATL 21 23 6
MIL 22 21 23
PIT 23 5 7
NYM 24 11 13
BAL 25 30 30
CHW 26 20 11
TOR 27 29 17
SD 28 17 20
HOU 29 18 12
OAK 30 22 27
0.3548387097 0.2013348165

Above is a chart that includes each team’s rank in FanGraphs Def statistic, their rank in Zone% (which is simply percentage of strikes thrown), and their rank in F-Strike% (first pitch strike percentage).

Taking a quick glance, a few things stand out. There does seem to be at least a bit of a connection, as the Red Sox and Royals do well across the board. Conversely, the A’s and Orioles rank poorly across the board. However, there are also teams like the Angels and Rockies whose metrics are all over the place.

When correlating Zone% and F-Strike% with the FanGraphs team defense ranks, it resulted in a positive correlation, but neither was high enough to cross into the realm of meaningful. Zone% had a 0.35 correlation with Def, while F-Strike% was even lower, at 0.20.

This is a bit surprising. It would certainly seem, from a distance, that a better defense leads to pitchers attacking the zone more frequently. While there may be some impact, neither correlation suggests it is anything approaching significant. Pitchers appear to be too set in their ways to care much about their defense.

Just look at the Reds. They have the second-best defense in baseball, but their pitchers are the second-worst in baseball at getting the first strike. Now part of that is that the Reds simply have bad pitchers, and that may be one of the biggest factors going against finding any real correlation here. Sure, Cincinnati pitchers may have more confidence to attack the strike zone, but if they’re just not good at doing so, there’s only so much impact that a defense can have. You could put a dozen Andrelton Simmons behind Robert Stephenson, and he still might struggle to get ahead in the count.

On the other hand, there may well be pitchers, like Sale, for whom a great defense behind them is extremely important, and not just in terms of turning balls in play into outs. Confidence is one of those squishy factors which has yet to be turned into a cold, hard statistic, but it is one that (seemingly) can often be found on display on the diamond.

It doesn’t appear that team defense can be called a major factor in pitcher confidence as of now, but that doesn’t mean it’s not worth digging into deeper, either on a more granular scale (e.g., changes in first pitch strike rate among individual pitchers) or even a wider scale (e.g., multiple seasons worth of fielding data might be more reliable, although it would be more challenging to account for roster changes).