TAMPA, Fla. -- Derrick Gainer scored an 11th-round knockdown and retained his WBA featherweight title Saturday night with a split decision over Victor Polo on the undercard of the Roy Jones Jr.-Derrick Harmon championship fight.

The decision was met by a chorus of boos from a crowd of 14,223 that jeered the champion for dancing most of the night to stay away from the more aggressive challenger from Colombia.

Judge Hector Hernandez scored the bout 114-113 for Polo. Judge Hubert Earle saw it 115-112 for Gainer, and judge Frank Skilbred favored the champion 111-109 in his first title defense.

Gainer, Jones' best friend from their hometown of Pensacola, improved to 37-5. He won the vacant WBA title with a technical knockout of Fred Norwood in New Orleans on Sept. 9.

Polo, who earned a shot at Gainer's belt with a 12-round unanimous decision over Angel Vasquez, dropped to 29-3-2 after his second loss in a title fight. In April 1999, he lost to featherweight champ Manuel Medina when the bout was stopped after the boxers bumped heads and Medina was ahead on the scorecards.

The close fight swung on Gainer's knockdown late in the 11th round. The fight ended with the champion slipping to his knees after raising his hands in celebration, a move that brought more boos from the crowd.

Light heavyweight Antonio Tarver, the 1996 Olympic bronze medalist at 178 pounds, rebounded from his only loss as a pro with a fifth-round TKO of Lincoln Carver (22-1, 18 KOs), who was knocked down in the fourth round and again midway through the fifth before the scheduled 10-rounder was stopped.

Tarver (17-1, 15 KOs) suffered a broken jaw and two broken ribs during a loss to Eric Harding in Biloxi, Miss., eight months ago. He hopes Saturday night's victory moves him closer to a potential shot at Jones' undisputed light heavyweight title.

Glenn Kelly of Australia stopped Billy Lewis at 2:17 of the 10th round in another light heavyweight bout.