Kell Brook has warned that Josh Kelly’s upcoming opponent David Avanesyan is “a real handful” who has “got better”.
Kelly is expected to challenge for Avanesyan's European welterweight title on a rescheduled date following the postponement of their March 28 fight, but Brook has questioned if he is a "complete fighter" yet.
Brook told Sky Sports about Avanesyan: "I've sparred with the guy and he's a real handful. You can give him some big licks but he keeps coming and he adjusts.
"He's a gate-keeper to see exactly where you are. And he's got better."
Russia's Avanesyan won three European title fights by knockout on away territory in Spain last year.
Former IBF welterweight champion Brook said: "Kelly is an amazing fighter, the skills are unbelievable. He is sharp, he has dummies. His technical ability? You can't hold a candle to him.
"In the amateurs we have four-round fights. Now it's 12 rounds.
"Against Robinson we saw him unravelling when it got past five or six rounds.
"You need to be a complete fighter - the heart, the chin, the toughness. You've got to have it all. When the going gets tough and he's questioning himself, has he got it? There's a question mark.
"Adam Booth is a very good trainer and [he will make Kelly's wrongs into rights]."
Kelly will be involved in his 12th pro fight but Brook, at the same stage in his career, hadn't yet reached British level.
He admits up-and-comers like Kelly are thrown into difficult fights much earlier: "It's a different era. So many of these fighters don't have time. If you can fight, show us. If not you get chucked to the wayside."
Avanesyan's promoter Neil Marsh warned at a fiery press conference: "I'm not talking [about a] 38, 39-year-old boxer, who's had his best days. You're talking [about] a kid who is in the best form of his life, who is hungry, whose total desire is to provide for his family, and that will be with beating Josh Kelly.
"I have got absolutely no doubt that Avanesyan knocks Josh Kelly out.
"It will be a difficult fight for five, six rounds. He's a fantastic amateur, he'll be moving a lot, he's got a lot of speed, but David is going to get to him."
Kelly replied: "I've got all this stacked up against us. I'm the underdog, I enjoy being the underdog."