ATLANTIC CITY, N.J. -- Wladimir Klitschko's chin betrayed him yet again, but this time his stamina didn't.
Klitschko, despite suffering three knockdowns before 10,137 on Saturday night at Boardwalk Hall, survived to outlast Samuel Peter and win a unanimous decision.
The 12-round verdict might not have restored Klitschko -- getting knocked down three times won't do that -- but winning the heavyweight title elimination bout earned him mandatory challenger status for the titles held by Chris Byrd and Lamon Brewster.
The victory didn't come without a serious struggle against the heavily hyped Peter (24-1).
The 24-year-old self-proclaimed "Nigerian Nightmare," had caught a big buzz in the boxing world with his string of exciting knockouts, but against Klitschko he was taking a big step up in competition.
He chased Klitschko (45-3) for most of the fight, looking to land one big shot. And he did just that three times, knocking Klitschko down twice in the fifth round and again in the 10th.
But Klitschko, whose weak chin and lack of stamina were exposed in stunning upset knockout loss to Corrie Sanders and Brewster, was able to survive.
"I have put my losses behind me," Klitschko said. "Boxing is a lot of fun, simple as that. I am ready to fight anyone."
In the end, all three judges scored it the same: 114-111.
"Peter was a very strong opponent, but he kept hitting me in the back of the head," said Klitschko, once considered the division's heir apparent, a role Peter had taken over before the fight.
"It's wonderful to be back in the heavyweight picture. Hopefully, I convinced some of the critics that I have the stamina to go 12 rounds."
Peter showed that his power is genuine and that he also had a solid chin, taking some big punches from Klitschko, the younger brother of heavyweight champ Vitali Klitschko. But Peter also was exposed as a one-dimensional fighter that Klitschko was able to outbox for much of the fight. By the end of the bout, the inexperienced Peter was also even more exhausted than Klitschko as he gasped for air.
"I took his best punch and knocked him down three times," Peter said. "I came to win but he did his best and he beat me. He beat me today, but maybe on my best day I can beat him. I learned from the experience of being in with a top opponent for the first time."
With a six-inch height advantage quicker hands, Klitschko was able to box, jab and move out of the way of the oncoming rush. But Peter pressured him so much, Peter was bound to land an effective blow.
It happened in the fifth, when Peter landed a clubbing right hand near the back of Klitschko's head. He went down face-first but was up at the count of six from referee Randy Neumann.
But 30 seconds later, Klitschko went down again on a half-push, half-right hand.
In the past, Klitschko fell apart under such adversity, but this time he willed himself through it.
Peter, still stalking in the 10th, cornered Klitschko and then chased him across the ring throwing shots until a straight right landed on Klitschko's chin and dropped him along the ropes.
Klitschko was up quickly but Peter continued landing until the bell rang.
Peter, his eyes swelling closed, still was gunning for a knockout in the 12th round. He was swinging wild lefts and wobbled Klitschko. But moments later, Klitschko landed a shot that buckled Peter, who was spitting blood in the closing seconds.
Dan Rafael is the boxing writer for ESPN.com