Afterwards, Williamson defeated Kendrick Releford by fifth-round TKO and Cuban contender Eliecer Castillo by majority decision before facing Wladimir Klitschko. The fight took place at Caesars Palace in Las Vegas, Nevada. Williamson dropped Klitschko forty seconds into the second round, but was unable to capitalize on it. An accidental head butt in the closing seconds of the fifth round caused Klitschko bleeding from a cut above his right eye. Due to the cut, the fight was prematurely stopped, with Klitschko being declared the winner by technical decision. Two of the judges scored the fight identically 49–46 in favor of Klitschko, while the third judge had Williamson winning 48–47.