Charlotte, NC (My Sportsbook) - Michael Phelps suffered his first defeat in a year, as world record-holder Aaron Peirsol won the 100-meter backstroke in a down-to-the-wire finish Saturday at the Charlotte UltraSwim Grand Prix.

Peirsol won the race in 53.32 seconds, barely edging Phelps (53.79), who a night earlier returned to competitive swimming for the first time since his record-setting Olympic gold medal haul last summer. Phelps had posted wins in the 200-meter freestyle and 100-meter butterfly.

This was the first time Phelps lost a race since May 17 of last year, when he was beaten by Peirsol in the 200m backstroke at Santa Clara.

Earlier Saturday, Phelps participated in the 50-meter freestyle preliminary heats and qualified for the next round but scratched himself from the final. The event was won by French world record-holder Fred Bousquet, who set a U.S. Open record time of 21.33 seconds. U.S. Olympian Cullen Jones came in second in 21.92.

Phelps, who won a single-Games record eight gold medals in Beijing, will race in the 100-meter freestyle on Sunday.