Another Look at Tom Glavine’s Generous Strike Zone

Jeff Sullivan recently suggested that despite his reputation Tom Glavine did not pitch to a significantly more generous strike zone. Sullivan points out Glavine did not get significantly more called strikes than other pitchers, even during the peak of his career. Sullivan’s analysis piqued my interest and made me wonder if Glavine’s reputation for getting a wider strike zone helped him succeed in ways beyond called strikes.

Glavine’s reputation alone likely influenced a batter’s behavior at the plate, encouraging batters who were behind the count to swing at questionable pitches. Batters believed if they did not swing these pitches would be called strikes for Glavine (when a batter swings at a pitch out of the zone when the batter is ahead of the count that has more to do with a pitchers stuff than the batter giving the pitcher an expanded zone). So, what would we expect from a pitcher who is getting batters to expand the strike zone? You would expect batters to make poor contact, yielding a lower BABIP. The batter would most likely swing at pitches outside the zone when the batter is behind the count.

Based on this reasoning, I hypothesize that Tom Glavine will see a greater reduction in quality of contact when he gets ahead of the count than a league-average pitcher. I’m going to look at the time span from 1991 to 2002 because that was the time span Jeff looked at and because I like palindromes.

To measure quality of contact I will be looking at BACON (batting average on contact). BACON is slightly different than BABIP because BACON includes home runs. If batters are expanding the strike zone when Glavine is ahead in the count we should see the quality of contact decrease. To measure the decrease in quality of contact, I will look at the ratio of BACON when Glavine is ahead to BACON to when Glavine is behind (the lower the number the greater improvement the pitcher experiences by getting ahead in the count). I will refer to this measure as EXP (a lower EXP shows a greater decrease in quality of contact, an EXP above 100 shows an increase in quality of contact).  The graph below compares Glavine’s EXP to the league average EXP for each season during the 11-year span.

 The league-average EXP is consistent year to year, hovering around 91, which suggests batters expand the strike zone for most pitchers when batters are behind in the count. Glavine’s EXP is not always better than the league-average EXP. In ‘94 and ‘96 Glavine was actually worse when ahead in the count than when he was behind.  This is to be expected because BACON takes a while to stabilize. Looking at Glavine’s data for a single season is subject to a fair amount of random noise because you have a relatively small sample of data. One season for Glavine gives us about 170 fair balls with Glavine ahead and 280 fair balls with Glavine behind. However, over a larger sample BACON stabilizes. At around 2,000 fair balls (more than in a single season for Glavine) BACON stabilizes. For example, when looking at the league-average EXP for a full year BACON is stable — with 3,500 fair balls with the pitcher ahead of the count and 4,600 fair balls with pitcher behind the count.

To make sure we are not just attributing skill to some random variation we need to look at a larger sample for Glavine. Over the 11 year span form 1991-2002 Glavine induced weaker contact (lower BACON) than the league average both when he was ahead of the count and behind the count. This is not surprising as we would expect a good pitcher to be better than average ahead and behind the count.  What’s interesting is Glavine has better than league-average EXP  (87 vs. 92) which suggests Glavine is better at expanding the strike zone than league-average pitchers. This comes with the caveat that while we have 3,056 fair balls when Glavine is behind the count, we only have 1,853 fair balls when Glavine is ahead — just shy of the 2000 at which the measure should stabilize.  Even so, the difference between Glavine’s EXP and the league-average EXP is very convincing.

Glavine (1991-2002)

MLB ave (1991-2002)

Ahead Behind EXP Ahead Behind EXP







To stabilize BACON, I increased the sample by looking at all the balls put in play. I compared balls put in play when the pitcher had two strikes to balls put in play when the pitcher had fewer than two strikes, which led to EXP2: the ratio of BACON when a pitcher has two strikes, to when he has fewer than two strikes. The table bellow shows a comparison of the quality of contact in two strike counts to non-two strike counts.

Glavine (1991-2002)

MLB ave (1991-2002)

2 Strikes Not 2 Strikes EXP2 2 Strikes Not 2 Strikes EXP2







Even with this larger sample size Glavine’s BACON is still lower than the league average in respective counts. More importantly, his EXP2 is still better than league average (although higher than his EXP).  Pitchers in general try to induce weaker contact when they are ahead of the count, but the data shows Glavine is doing something special to induce even weaker contact.

Is Glavine getting batters to give him a wider strike zone? We cannot definitively say what is causing this pattern in the data, but we are seeing the type of numbers we would expect to see if the batter was giving him a wider strike zone.


All splits number are from Baseball-Reference.

George is always thinking about baseball, and frequently writes down those thoughts on his blog. Follow him on Twitter @GWRambling.

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8 years ago

Glavine sure brought home the BACON.

Matthew Cornwell
8 years ago

It is pretty evident that Glavine was the rare outlier who had significant impact on all three of the “luck” factors: BABIP, LOB% (or sequencing), and HR/FB. The weird thing is, he wasn’t an extreme FB pitcher, and extreme GB pitcher, or a K pitcher – the types who usually have those kinds of abilities. I think this ability to expand the zone, hit his spots, and exploit hitters’ eagerness to be heroes explains much of it. Glavine had pretty normal BABIP, BB/K rates with nobody on base, actually and Hhs HR rate was still really good here too. But with men in scoring position, he threw further and further away from the plate. This did the following for him:

1. With batted ball contact so far outside, he caused a major disproportionate amount of opposite field flyballs compared to average and as we know opposite field FBs become HRs at a much lower rate. This explains much of his wildly low and consistent HR/FB rate and why he rarely coughed up HRs with men on base (sequencing).
2. His BABIP dropped 10-15 points with RISP. This and his own great defense were the driving forces behind his BABIP. Not only were the batters making worse contact with RISP by swinging at balls further off the plate, but the Braves were able to shift the infielders towards the right side of the field. This is another key element to his LOB% ability.

This pattern holds true: when he was behind vs. ahead, small scoring margins vs, large scoring margins, with no outs compared to two outs, and on and on and on. Any question if it was intentional should be squashed.

8 years ago

What is this talk of Glavine “doing something special to induce weaker contact”? I thought, based on the work of Voros McCracken and others, that pitchers could do no such thing! I thought that it was accepted within the sabermetric community that pitchers had no control over producing ‘weak” contact. I thought that advanced research had shown that pitchers could control only these things: strikeouts, walks, and home runs. Now, I do not agree with this McCracken/Sabermetric conclusion. My perception tells me that some pitchers-perhaps many or most successful pitchers–have a repeatable skill of being able to miss the sweet part of the bat, i.e., induce weak contact. But Fangraphs puts out this article seeming to contradict my understanding of saber metric orthodoxy! Am i misunderstanding either this article or the McCracken research? Just trying to learn–thanks–
Tony Dyer

Matthew Cornwell
8 years ago

Very few people still hold to a strict Voros-DIPS philosophy. The issue isn’t that pitchers have no impact on BABIP, but that the range in talent at the MLB level is so relatively small compared to ranges in K and BB, etc., that it is hard to find the true talent without a large sample size. And BABIP that is way better or worse than league average will very likely regress towards league average the next year.

But over the course of a long career, the signal can be found in the noise, and we can see a pitcher’s BABIP skill. Have you not seen any BABIP research the past 10 years?