Interesting revisionist history. There's no difference in Sabathia's velocity or peripherals from 2007 with Cleveland and 2009-2011 with the Yankees. When he started changing as a pitcher was last year. From 2007-2011 (as far back as pitchfx goes on fangraphs), Sabathia averaged 93.82 mph on his fastball, his fastball had a positive win value, and his HR/FB% was always below 9%. In 2012, Sabathia lost 1.5 mph on his fastball, his fastball had the worst win value of his career, and he had a career high HR/FB of 12.5%. Then, this year his fastball lost an additional 1.6 mph on his fastball, his fastball win value has been the second worst of his career, and he's posting a new career worst HR/FB% of 14%.
This isn't something that happened overnight. In the last two years, he's lost 3.1 mph on his fastball and posted the two worst HR/FB% of his career. Does that mean his career's over? Of course not. He's still a solid #2 or #3 starter right now. But whether he'll remain a solid #2 or #3 pitcher if he loses another 3 mph on his fastball is yet to be seen. Someone who's posted back to back years of the worst home run rate of their career is not someone who's made the adjustment to pitching with diminished velocity.