Looking at the Fangraphs data, Cookie has been transitioning from primarily a fastball pitcher to primarily a breaking ball pitcher for about seven years. In 2013 he threw 62.6% fastballs averaging 95.6 mph and his percentage has been steadily declining since. This year he's throwing the heater only 39.1% with an average velo of 93.9. He's only lost 1.7 mph but he either doesn't have as much confidence in it or he feels he's more effective throwing more breaking balls.
His strikeout rate is the highest of his career at 29.2%, nearly 4% higher than his career average. But his walk rate of 11.2% is well above his career figure of 6.3%. He's throwing a lot of sliders and changeups off the plate resulting in more K's but also more walks.
There was a great example last night where he got ahead 0-2 and threw three sliders in the dirt. On the 3-2 pitch he threw another slider in the dirt and got the hitter to chase. Cookie would rather walk the guy than throw him a 3-2 fastball in a 1-0 game.
Hitters are catching on. The rate of swings at pitches outside the zone is 30.1%, down from 36.6% and 36.4% the last two years and 34.4% for his career. So his walk rate is up as batters are learning to lay off the breaking stuff down and away. His xFIP is the highest since 2013 at 4.15.
I'm not sure how long he'll continue to be effective as a starter depending mostly on breaking balls and getting hitters to chase the off-speed stuff. He seems to lose fastball velocity in the 4th and 5th innings. He starts the game at 94-95 and ends up at 92. If he can locate his fastball on the edges and throw it when batters least expect it I imagine he can continue to be a solid MOR starter.
