Here's MLB legend Jeff Bagwell happy as hell he's not on the Yankees right now ... 'cause he tells TMZ Sports the way Gerrit Cole is currently pitching is straight-up scary!!
"He's the closest thing I've seen to Randy Johnson," the Astros legend says ... "He's tough. He's a monster out there."
Cole has been mowing down lineups all season ... and nothing's changed so far in the playoffs -- especially in Houston's HUGE Game 3 win over the Yanks on Tuesday.
Bagwell -- one of the greatest power hitters ever -- says it's truly impressive what the flamethrower has been able to do over the last few months.