First reign as WBA heavyweight champion In 2005, Valuev squared off with WBA heavyweight champion
John Ruiz, and won a twelve-round majority-decision, becoming both the tallest (7 ft or 2.13 m) and heaviest (324 lbs or 147 kg) champion in boxing history.
Valuev vs. Chagaev , 2007 The title defense was held on 14 April 2007. Chagaev defeated Valuev by a majority decision (117–111, 115–113 and 114–114). Valuev changed trainers, from Manuel Gabrielian to Alexander Zimin, who coached the old Soviet Union amateur boxing team. On 29 September 2007, Valuev won against
Jean-Francois Bergeron in
Oldenburg,
Germany, by a 12-round unanimous decision (118–111 on all three cards).
Between title reigns Valuev vs. Liakhovich On 16 February 2008, in a title eliminator, Valuev defeated former titleholder
Siarhei Liakhovich, winning every round at the
Nuremberg Arena in
Germany. The victory earned Valuev the right to face Chagaev for the WBA title again, the only man who had defeated him in his boxing career.
Second reign as WBA champion Valuev vs. Ruiz II He was scheduled to face Chagaev for his WBA title on 5 July 2008, but Chagaev pulled out with an injury. Valuev instead fought John Ruiz for the vacant title on 30 August 2008 and the
WBA decided to make Chagaev "Champion In Recess". Valuev defeated Ruiz by unanimous decision to regain the WBA heavyweight championship, with Valuev and Chagaev set to fight no later than 26 June 2009 to determine whom the WBA regarded as their champion. The scores were 114–113, 116–113, and 116–111. The result was initially declared a split decision win for Valuev with the 114–113 score by ringside judge Takeshi Shimakawa was announced in favor of Ruiz rather than for Valuev. One of the scorecards had the names of the fighters in opposite order, resulting in the confusion. The decision was once again unpopular with the live crowd, as some booed the outcome, much like in the first bout.
Valuev vs. Holyfield Valuev's first title defense of his second reign as WBA Champion was against the 46-year-old, four-time heavyweight champion of the world,
Evander Holyfield, on 20 December 2008. Before the match, Valuev weighed 310.8 pounds (141 kg), nearly 100 pounds heavier than Holyfield at 214.3 pounds (97 kg). After a rather uneventful match with no knockdowns and few punches thrown by either fighter, Valuev won a widely disputed majority decision. In response to the controversial result the WBA announced plans to investigate the decision.
Loss to Haye In his second defense on 7 November 2009, billed as
David vs. Goliath, Valuev faced off against former unified and lineal
cruiserweight champion
David Haye (22–1, 21 KOs) at the
Arena Nürnberger Versicherung in
Nuremberg. Valuev lost by a majority decision (114–114, 116–112, 116–112).
Retirement from boxing and health problems Valuev announced his retirement from boxing in a Russian newspaper three days after the loss to Haye on 10 November 2009. In 2010, Valuev's doctor went on record saying that he is treating Valuev for "serious bone and joint problems". Valuev underwent two operations that required at least six months on the sidelines. Valuev confirmed in 2013 that medical advice was one of the reasons he is not planning to make a comeback in boxing. ==Outside of boxing==