Maccarinelli's next fight was an all-British unification fight against the WBA/WBC champion David Haye. The fight took place on 8 March 2008 at the O2 Arena, London and was much hyped in the weeks running up to the event, being given the tagline "bombs away" (referring to the high KO percentages and punching power both men boasted). Maccarinelli lost the fight and his WBO belt when he was knocked out in the 2nd round. A right hand by Haye knocked Maccarinelli down towards the end of the round and although he was able to get back up it was on unsteady legs and the referee stepped in to stop the fight.