According to Brooks Baseball, his average fastball of 96.3 over last month is the lowest velocity he's had in over 10 years. It's down a full mph since June.
He had a handful of 94 mph tonight. He was consistently at 97 with the Cubs and now he's only reaching that once in a while. I saw plenty of 98-99 from him earlier in the year.
But Kimbrel is supposed to be good enough to not have to worry about getting squeezed or facing a slugger. His fastball command has been garbage, the velocity is down and hitters are crushing it.