Here's Dodgers reliever Joe Kelly giving a whole new meaning to "breaking ball" ...
The L.A. pitcher was working on his off-speed stuff in an at-home, quarantine throwing sesh this week ... when he let one get away from him -- and threw the cowhide straight through a window!!!
Yeah, JUUUUUUUUUUUUSTTTT a bit outside!!!
You can see in the footage of the aftermath (filmed by his wife) ... the damage Kelly's changeup did was pretty significant.
There was glass everywhere and a big ol' hole through the window ... and JK sure seemed to be is disbelief over it all.