If Conor McGregor really wants to continue his boxing career he might've found his huckleberry ... former welterweight champ Danny Garcia, who says he'd beat Conor's ass ... worse than Floyd did.

McGregor has publicly stated he thinks he'd win a rematch with Floyd, and hasn't ruled out a return to the boxing ring in the future (why not? He reportedly made more than $100 million last time).

We got Danny at Team Watson Boxing in L.A. (where huge fighters train), and he said he's more than willing to kick the damn hell out of Conor, and thinks he'd finish him way faster than Floyd did.

"He ain't going 10 rounds with me, I'm a seek and destroy type fighter, I'm one of the type of fighters you want to run from when you fight, it ain't going past 4."

That's an old-fashioned call out from a legit star ... your move, Conor.