R.I.P. Brian Wilson's luscious, strong, beautiful beard ... 'cause the MLB pitcher says his face-warmer is officially gone forever.

Probably. 

The ex-SF Giants/Dodgers fireballer was lookin' all jacked in L.A. this week -- sippin' on a blender full of  a healthy-lookin' drink -- when we noticed his face was much more bare than we were used to. 

FYI, Wilson's reportedly attempting an MLB comeback as a knuckleballer. 

And by the look of his stubble, the beard is also trying to make a comeback. 

Fingers crossed for both.