Well, this guy knows -- he's Conor's training partner -- and tells TMZ Sports the raw power is strong enough to OBLITERATE every bone in Khabib's body.

Meet John Redmond -- a pro MMA fighter who trains with McGregor at the legendary Straight Blast Gym in Ireland.

In fact, you might remember John as the guy who was fighting at Bellator 187 last year when Conor jumped into the cage and started going berserk on the ref. Good times ...

Now, John says Conor is just too strong, too skilled and too experienced for Khabib -- HE'S GONNA SMASH THE GUY!!

"Khabib, he has a record of 26-0 but he's fought a lot of bums along the way," Redmond says.

"He's never fought a precision striker who can put a shot on your jaw and leave you unconscious."

"I've been in the cage with Conor, I've felt his power, I've felt his shots. The guy's not coming to play around here."

Watch the clip ... John says this fight's over in the FIRST ROUND -- when Khabib meets a particularly violent end.

BTW, John didn't make the trip out to Vegas -- he stayed in Ireland where he says the entire country is going crazy and pounding Conor's whiskey to gear up for UFC 229.