David Haye insists whatever happens in the second Carl Froch-George Groves showdown at Wembley on May 31, the underdog has proved he belongs on the world stage.
Groves was once a stablemate of Haye, sharing trainer and manager Adam Booth at their south London base, but he chose to split with Booth to join up with Irishman Paddy Fitzpatrick's gym in Swindon a week before the first fight with Froch.
Former world heavyweight champion Haye has tracked Groves' career from his early amateur days and, speaking on Ringside, he claimed the west Londoner forced everyone to take him seriously with his performance in the first bout with Froch.
Groves was controversially stopped in the ninth round of that Manchester thriller in November and Haye said: "I know them both very well, I've known them for many years.
"I know George has come from a good amateur to a world-class boxer, and I've seen that behind closed doors. Before the fight with Carl everyone said 'it's going to be a blow-out job, he's only fought at domestic level'.
"I said 'okay, he's only ever fought at domestic level but behind closed doors he's been sparring', he used to spar my sparring partners and I'd seen him handling heavyweights and cruiserweights, former world champs.
"He'd been (ably) handling them in the gym but never translated that to competition, so I knew he could do it physically, I wasn't so sure he could in the ring.
"He showed Carl in the first round, he proved he can perform at the highest level, when he's being booed, when he's the underdog.
"He's come of age as a worldwide, recognised world (class) opponent. As soon as you recognise that it gives you that confidence. Carl's already got it, he's had it for many years, but it makes this fight really interesting."
Haye, whose own fight future was thought to be over after reconstructive shoulder surgery late last year, feels the second clash between the two foes is still too close to call.
Nottingham fighter Froch will put his World Boxing Association and International Boxing Federation super-middleweight titles on the line against Groves in the highly anticipated second clash, this time in London, live on Sky Sports Box Office.
Haye added: "There's two schools of thought: George 100% knows (his ability). Before he thought it but didn't know it. Now he knows he's world class and that gives you that advantage going into the second one.
"For Carl, he didn't take George seriously, he didn't believe he was world class. I know it, he pretty much told me that. But he knows now. So now he's going to be preparing for a world class opponent, mentally.
"Physically Carl is always in great shape. But it's mentally, going to sleep knowing 'my whole life's on the line, I could be knocked out!' So you've got an argument for both guys."