Daniel Cormier's fought Jon Jones, Stipe Miocic, Rumble Johnson and Derrick Lewis ... and when it comes to grappling, Khabib's stronger than every one of them.
DC came into the TMZ offices earlier this week and joined the guys on the "TMZ Sports" TV show (airs weekdays on FS1) ... and we asked him about his training sessions with Khabib.
DC and Khabib are close friends and gym mates at American Kickboxing Academy (AKA) in San Jose, CA ... and they've trained together for years.
So, how does the 155-pound UFC lightweight champion fare against the 250-ish-pound heavyweight champ?
"The other day we started to grapple, and Khabib jumped on top of me. And, I'm like okay, I'm just gonna get up when I want to, but that is not the case," Cormier says.
"He is literally the strongest person I may have ever felt."
DC -- who's facing off with Stipe Miocic at UFC 241 on Saturday -- says when Khabib gets a hold of you, it's basically impossible to get loose.
"It was amazing to me to think a guy that weights 175, 180 pounds, was able to do that to me. It's positional control, it's strength. He's a phenomenal athlete, man."
"And, just one of the greatest stars mixed martial arts has ever seen."