Madison Bumgarner went ballistic on Cardinals star Willson Contreras during their game on Wednesday ... telling the St. Louis catcher to "shut the f*** up" -- while appearing to call him a "p****."
The Diamondbacks pitcher fired off the NSFW commentary after Contreras got mad at himself for fouling off a pitch in the third inning.
It's unclear exactly why the former World Series MVP was so ticked at Contreras for the reaction ... but a hot mic captured almost the entirety of his ensuing rant.
"Shut the f*** up," Bumgarner can be heard saying on the game's broadcast .