Make some room in Cooperstown for Justin Crawford in about two decades -- 'cause Johnny Damon says the Philadelphia Phillies' top draft pick is about to have a MONSTER MLB career!!
Damon -- who used to play against Justin's father, Carl Crawford, in The Show -- made the guarantee to TMZ Sports while out at an event in NYC earlier this month.
"He'll probably steal 500 bases," Damon said of Justin, "hit a couple hundred home runs. Just be a menace to his opponents throughout the years.