James DeGale has warned fellow Briton Nathan Cleverly to expect a tough night against Badou Jack on Saturday.
Welsh light heavyweight Cleverly faces Jack in the chief support fight to Floyd Mayweather Jr's light middleweight boxing contest against mixed martial arts fighter Conor McGregor at the T-Mobile Arena in Las Vegas on Aug. 26.
Sweden-born Jack, who lives in Vegas and is promoted by Mayweather, is fighting at light heavyweight for the first time after being held to a points draw with DeGale in a world super middleweight title unification clash in January.
In one of the best fights this year, DeGale was down in the last round and Jack in the first. DeGale also finished the fight minus a bridge of false teeth -- knocked out by a punch -- a broken nose, a perforated eardrum and needed stitches to a facial wound.
"This is a very hard fight for Nathan," said DeGale. "It's going to be a good fight, an entertaining fight, the styles gel.
"Jack always brings it, Cleverly is never in a dull fight, so the fans are going to be happy. But it's a hard fight for Nathan."
DeGale, the IBF world super-middleweight champion, is flying out from England to be in Vegas to be at the much-hyped Mayweather-McGregor.
And as Jack's last opponent, DeGale hopes to be able to speak to Cleverly in Vegas before fight night to pass on advice.
"I haven't spoke to Nathan, I will probably see him in Las Vegas so I will speak to him then," said DeGale. "I can't really judge how good Badou Jack is at the moment because I was injured when I fought him.
"I know Jack is a good fighter, he's got some good wins on his record, he has beaten a couple of good people, but the Cleverly fight will tell me a lot more about Badou Jack.
"If he can get in there and deal with him I will know he is a serious contender."
As for the main event, DeGale is dismissive of McGregor's chances yet will still fly out from London to Las Vegas to be at the fight between a generation's best boxer, who is now 40 years old, and a mixed martial arts fighter who has never boxed professionally.
"It's a mismatch if I'm being honest," said DeGale."It's going to be a great event, it has made for a fantastic build-up with McGregor because he's just as interesting a character as Mayweather.
"But it's a mismatch. One of boxing's greatest fighters against a complete novice, a guy who has never had a professional boxing bout in his life.
"I can see Mayweather stopping him late on or it being a whitewash and him winning every second of every round.
"I'm going, if I'm being honest, because my advisor Al Haymon invited me and because they are two big characters.
"I like McGregor as well, I like the way he gets down, I like his attitude, his self-belief and the way he fights. Mayweather is one of my favourite fighters, so I want to be there to experience the atmosphere. It's going to be one hell of an event but it's only going one way."
DeGale, who is recovering from shoulder surgery and targeting a December ring return, says Mayweather-McGregor could be the start of more boxer-versus-UFC events.
"I can see a lot of people from boxing and UFC fighting each other. I'm looking for my middleweight, who is it?" added DeGale. "That's how it's going and Tony Bellew and Michael Bisping have been talking about it this week.
"If I got in an Octagon with whoever is the champion in my weight he'd end up winning. I'm not into all the kicking and wrestling. But if he got in the ring with me he wouldn't last two rounds.
"They're two different sports. It could be a thing that's going to start happening but boxing wins every day."