It's more complex than this, but teams have stopped swinging. They know that his command hasn't been pinpoint like it was last August, but they also know the stuff is still insanely hard to hit. So if they get ahead in the count they shrink their zones to nothing and hope that he doesn't fool them or he can throw 3 balls before he throws 3 strikes. Arrieta is in about the same number of 1-0 counts as last year, ~40% of total PA. 2015 after 1-0: 345 PA, .188/.257/.287, 8% BB% 2016 after 1-0: 153 PA, .206/.346/.310, 16% BB%