Umpires have a difficult job, but we expect them to be professionals. As such, we expect them to constantly review their performance and look for ways to improve. They should not be dismissing anecdotal evidence or hunches; those are great places to start looking.
A little while ago I looked at some data that suggested that Jays pitchers get squeezed more than their AL East counterparts.
This was while the Jays were treading water in the month of April.
Bad strike zone calls have two effects: the obvious (directly affecting ball-strike count for hitters and pitchers) and the secondary effect of messing up pitchers and hitters - tight strike zones lead to pitchers grooving pitches down the middle; low strike zones lead to more ground balls, and high strike zones lead to more strikeouts.
It's important that the strike zone be called in a fair and equal way to both teams. Umpires aren't perfect machines, but we should at least expect consistency.
The data, unfortunately, suggests otherwise.
In recent days, it's been observed that umpires may be calling different strike zones for and against the Jays.
To see if the data supports this using Pitch F/X data, we look for balls that are called strikes, and strikes that are called balls, for and against the Jays.
Apr (12-15) - 246/4142 Jays' pitches are balls called strikes (5.9392%), 288/4046 pitches against Jays' hitters are balls called strikes (7.1181%)
May (21-9) - 261/4434 (5.8863%), 270/4422 (6.1058%)
Jun (12-15) - 191/3850 (4.9610%), 280/4007 (6.9878%)
Jul (2-3) - 27/718 (3.7604%), 44/721 (6.1026%)
This suggests that Jays' pitchers get squeezed more than their opponents. Only in May was it about fair - and that's the Jays' only winning month.
Looking at the corollary (strikes called balls),
Apr (12-15) - 76/4142 Jays' pitches are strikes called balls (1.8349%); 840/4046 pitches against Jays' hitters are strikes called balls (0.9886%)
May (21-9) - 57/4434 (1.2855%), 58/4422 (1.3116%)
Jun (12-15) - 41/3850 (1.0649%), 48/4007 (1.1979%)
Jul (2-3) - 14/718 (1.9499%), 12/721 (1.6644%)
May and June were good months for Jays' pitchers, and they were also getting squeezed less (almost half as much!). Jays' pitchers were especially getting squeezed hard in April compared to their mound opponents, almost twice as much.
In May, the calls became even, and in June, the calls became slightly favorable to Jays' hitters.
BTW, note how the Jays' hitters seemed to be extra patient in June, seeing almost 150 more pitches than their opponents for the month. In a small sample size in July, the calls are now going against the Jays. If not for Kawasaki's five strikes called balls, the Jays hitters would be half as lucky as their opponents in June.
In summary, Pitch F/X suggests that the strike zones are different for the Jays vs. their opponents.