Guinn, once described as "hot prospect" and viewed as one of the top-rising American heavyweight contenders,[11][12] was 3–2–1 in his last six fights, losing to James Toney and Tony Thompson by unanimous decisions but defeating then-highly regarded prospest, Olympic Gold medalist Audley Harrison.
[13] The win over Dominick Guinn earned Chambers a spot in the 4-man elimination tournament to face Wladimir Klitschko for the IBF world heavyweight championship.
In the final, which took place less than three months later, Chambers faced undefeated Alexander Povetkin, who had beaten former IBF world champion Chris Byrd in semifinals by eleventh-round TKO.
Chambers was doing the better work in early rounds, landing cleaner, harder shots, but was eventually overwhelmed by Povetkin's relentless pressure.
[22] Prior to facing Chambers, however, Peter had lost the world championship to Vitali Klitschko, and was looking to bounce back to the heavyweight title picture.
[25][22] A win over Peter lined Chambers up to fight 6 ft 7in tall, undefeated Alexander Dimitrenko on July 4, 2009 in a WBO world heavyweight title eliminator.
Coming into the bout, Dimitrenko had scored five stoppages in a row, with his most recent win against popular German boxer Luan Krasniqi.
[29] Unlike his previous fights, Chambers was the aggressor, taking the centre of the ring and constantly pressing Dimitrenko against the ropes.
[35] In the pre-fight comparison of the fighters, The Ring gave Chambers the upper hand in speed and athletic ability, as well as defense, while crediting Klitschko as more powerful and experienced.
[34][36] The bout turned-out to be one-sided, with the champion winning rounds keeping Chambers at the end of his jab and occasionally throwing straight right hands.
[38] Chambers returned to the ring almost eleven months later, defeating Derric Rossy again, this time by unanimous decision, in an IBF title eliminator.
[40][41] Chambers claimed to have problems with his back for an extended period of time, and that it finally caught up to him during preparation for the Thompson fight.
[42] He was then due to face former WBO world heavyweight champion Siarhei Liakhovich on 21 January 2012 at Asylum Arena in Philadelphia, in the inaugural main event of the Fight Night card televised by NBC Sports, but was forced to withdraw after fracturing his ribs during training camp.
During the first round, Chambers torn his bicep in the left arm,[47][48] and often switched between orthodox and southpaw stances throughout the rest of the fight, throwing shots almost exclusively with the right hand, mostly connecting with overhand punches.
Chambers made his return to the ring fourteen months later, moving down to cruiserweight to fight South African contender Thabiso Mchunu.
Having had fought only twice in three and a half years prior to the bout, Chambers gave a relatively poor showing and lost the fight by unanimous decision.
[citation needed] Former sparring partner and team member Tyson Fury came on record defending Chambers saying that Joshua finally showed his true colors.
[citation needed] On February 7, 2023, at age 40, Chambers made his return to the ring after a near 7 year lay-off with a 3rd-round TKO victory against Corey Williams.
Per trainers James Ali Bashir and Steve Upsher, Chambers will look to compete at heavyweight but keep close attention to a newer WBC weight class of bridgerweight, which falls between 200 and 224-pounds.