On May 7, 2011, Pacquiao successfully defended his WBO Welterweight title against three-division world champion Shane Mosley via lopsided unanimous decision at the MGM Grand Arena. Rapper LL Cool J performed as Mosley first entered the arena, while vocalist Jimi Jamison of the rock band Survivor sang "Eye of the Tiger" as Pacquiao approached the ring. Pacquiao knocked Mosley down in the third round using a one-two capped with a left straight. Mosley was left dazed by the knockdown but managed to stand up.[109] Mosley floored Pacquiao in the tenth round with a push, but referee Kenny Bayless inexplicably ruled it a knockdown. None of the judges seemed to have bought it judging from the scores. Replays showed that Pacquiao was throwing a punch off balance, had his right foot stepped on by Mosley's left foot and went down with a little help from Mosley's right hand. Bayless apologized to Pacquiao after the fight for the mistake. Pacquiao gained one-sided verdicts from all three judges 119–108, 120–108, and 120–107.[110] Pacquiao reported that the only thing preventing him from knocking out Mosley was a cramp in his legs. Freddie Roach said that Pacquiao had problems with cramping before but usually in training sessions and not in the middle of bouts.[111] After the fight, there was much controversy over Shane Mosley reportedly telling Floyd Mayweather that he should have made Pacquiao "take the test.

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