Countdown 2005 and won via submission in less than two minutes. Overeem lost in the semifinals to the eventual champion Maurício Rua. In February 2006, Overeem fought Russian Top Team favourite Sergei Kharitonov. Overeem won, dislocating Kharitonov's shoulder in the process. With his win over Kharitonov, Overeem secured a spot in the PRIDE 2006 Openweight Grand Prix at Pride Total Elimination Absolute. He fought Brazilian jiu-jitsu specialist Fabrício Werdum, and lost via kimura in the second round. Debut in Strikeforce On 9 June 2006, Overeem travelled to San Jose, California, to win a rematch with Vitor Belfort by decision at Strikeforce: Revenge. Return to PRIDE A month later Overeem returned to PRIDE for a highly anticipated rematch with Antônio Rogério Nogueira. Overeem entered the fight with a heavily taped neck. After controlling the first round and a half with his striking, Overeem was stumbled from a punch, and Nogueira followed with a flurry of strikes. Worried Overeem would be more severely injured, his corner threw in the towel. At Pride Final Conflict Absolute, Overeem lost to Ricardo Arona. Overeem was on the receiving end of a leg kick that caused a non-serious injury to his nerves, causing him to lose feeling in his foot and leg. Unable to mount much offence or defend against Arona, Overeem tapped out to avoid further injury. He then suffered another KO loss to Maurício Rua at Pride 33, but returned in June 2007 with a submission win over Michael Knaap at K-1 Grand Prix in Amsterdam (despite K-1 being a kickboxing promotion, the bout was fought under MMA rules). On 17 September 2007, at the Hero's 10: Middleweight Tournament Final, Alistair faced Sergei Kharitonov again. Overeem showed solid movement as soon as the first round began, but he suffered a KO loss just before the end of the first round. Return to Strikeforce/DREAM/Dynamite On 16 November 2007, Overeem defeated Paul Buentello for the vacant Strikeforce Heavyweight Championship by submission due to knee strikes. On 15 June 2008 Overeem won by KO in the first round against Lee Tae-Hyun at DREAM 4. On 21 July 2008, Overeem defeated K-1 World Grand Prix Champion Mark Hunt in the first round by submission at Dream 5: Lightweight Grand Prix 2008 Final Round. His next fight was against Mirko Cro Cop at Dream 6 on 23 September 2008. The bout was stopped about halfway through the first round