I was wondering about the same thing.
Depending on how much stock you put in DRS, the Jays are #1 in the league this year with 82 defensive runs saved, compared to 44 last year. A simple calculation of the difference over the course of the year would be about -0.24 per game to the pitching rotation's ERA. Not small potatoes. With all other things being equal, that's the difference between Kikuch having a 3.82 ERA with this year's defence vs. a 4.06 ERA with last year's.
Not sure if this holds water, but seems to pass the sniff test.