LOS ANGELES (AP) — Floyd Mayweather Jr. says Andre Berto is a worthy opponent for the final fight of his perfect career.

Three months after Mayweather (48-0, 26 KOs) dominated Manny Pacquiao in the most lucrative fight in boxing history, he began the difficult business of promoting his pay-per-view bout with Berto on Thursday with a news conference in downtown Los Angeles.

Mayweather acknowledged the immediate backlash from his choice of Berto (30-3, 23 KOs), a former welterweight champion who has lost three of his last six fights. Mayweather promises an exciting fight, even guaranteeing somebody will get knocked down.

Mayweather also repeated his declaration that this is the last fight of his career, although he grinned broadly while saying it. He also retired in 2008, but now says that was "only a vacation."