For the second night in a row, Maryland swimming sensation Michael Phelps was decisively beaten in a key race at the U.S. Olympic trials by a rival who set a world record.

In his last of 17 races during the eight-day trials, Phelps, 19, was beaten by Ian Crocker, 21, in the final of the 100-meter butterfly on Tuesday. Crocker finished in 50.76 seconds, breaking his own world record of 50.98 seconds. Phelps finished in 51.15 seconds.

Crocker, a fast starter, rocketed to the lead early and Phelps, a potent finisher, didn't catch up. Phelps blamed his defeat on his start and turn.

"He definitely took me out in the first 50 [meters] and I was just too far behind him," Phelps said. "I couldn't catch up to him."

It was the second loss in as many matchups between Phelps and his two chief rivals. Monday night, Phelps came in second to Californian Aaron Peirsol in the 200 backstroke.

It also cast some question on Phelps's quest for seven gold medals at the Olympics, a feat that would match the accomplished by Mark Spitz in 1972 and earn Phelps a $1 million bonus offered by Speedo, Phelps's main commercial sponsor.

Although Phelps's coach, Bob Bowman, believes his swimmer could still win both events at the Olympics next month in Athens, losses could narrow his chances for seven golds.

Phelps did, however, swim an arduous program here, and in the process became the first American male to qualify for six individual events at the Olympics.

"When you are racing against Michael, nothing is given," Crocker said. "Michael's a phenomenal swimmer, and he's trying to do something really special."

Crocker, who wore a black and gray ankle-length suit, is tall, blonde and quiet. Phelps, who was in a blue and gray ankle-length suit, is tall, dark-haired and generally lighthearted. Crocker likes Bob Dylan; Phelps loves rap.

Crocker, a native of Portland, Maine, narrowly beat out Phelps for the world record of 50.98 seconds last summer. Phelps was stung by the defeat and has had a magazine photo of Crocker hanging in his bedroom as motivation ever since.

Phelps got a measure of revenge May 22, when he edged Crocker in the event during a meet in Santa Clara, Calif., finishing in 52.39 seconds to Crocker's 52.56.

But in semifinal races Monday night, Crocker's time of 51.25 was better than Phelps's 51.89. Phelps's race, though, was the last of three events he swam that night in very short order, and Bowman said he was amazed at his swimmer's time.

Crocker is soft-spoken, thoughtful and serious. He said he tries not to think about his competitors. "I'm strictly out for speed," he said earlier this week. "I love going fast. I love surprising myself. . . . That's my thrill."

He said before the faceoff with Phelps that he was not yet in peak condition, and was looking forward to Athens, "no matter what the outcome is here."

"I think that I can really surprise myself and other people in Athens," he said.

Eddie Reese, who is Crocker's coach at the University of Texas and the coach of the U.S. men's Olympic team, said Tuesday that despite his cerebral demeanor Crocker "is a guy with a killer instinct."

For Phelps it was also his only race of the day during a meet in which he twice swam four times a day, and once swam three times in a single session.

People were still talking here Tuesday about Phelps's triple-play performance Monday night. Even though he lost the backstroke, he came back and easily won the final of the 200 individual medley, and his semifinal 100 butterfly in very fast times.

"There's nobody in the world that can do that," said Reese. "It was amazing."

Bowman said he was satisfied with Phelps work.

"He's shown that he's on his way to top form," he said. "Our goal is to swim at his best in the Olympic Games, and I think he sort of made this a good step toward that."

He did say that he would rethink Phelps's plan of action for Athens. He said he had to declare the program by Thursday to Everett Uchiyama, the national team director for USA Swimming, the sport's governing body. Uchiyama said the Olympic programs would be couriered to Athens by the end of the week.

Phelps entered six individual events here. He holds the world record in the 200 butterfly and the 200 and 400 individual medley, and won those events here. Bowman indicated that Phelps would swim those in Athens.

Phelps also won the 200 freestyle here, but Australian swimmer Ian Thorpe has a firm grip on that world record. Phelps also had his sights on the 200 backstroke and 100 butterfly.

"It's a big program," Bowman said Tuesday, "particularly if you add the relays to it, then it becomes really big. So maybe it's in [Phelps's] best interest" to drop one event.

"He's clearly fatigued; I think it showed a little bit tonight," Bowman said.

Bowman said he was mostly rethinking the 200 freestyle and 200 backstroke. They held "the least likely odds for a gold medal," Bowman said. He said he thought Phelps's butterfly is sound.

Reese said he hoped Phelps would stick to swimming six individual events.

There are also three Olympic relays, the 400 freestyle, the 800 freestyle and 400 medley relay. The relays were not on the program here. Bowman wants Phelps on all three. The decision on the final relay makeup will be complicated and won't be made until the Olympics.

Ian Crocker reacts after setting a world record in the 100-meter butterfly with a time of 50.76 seconds. Crocker also beat Michael Phelps in the race.Ian Crocker, 21, is on his way to a world-record time in the 100-meter butterfly in the U.S. Olympic trials. He beat Michael Phelps for the second time in a major race.Michael Phelps had reason to smile after he became the first American male to qualify for six Olympic individual events. Overall, he swam 17 races in 8 days.