OMAHA, Neb. — Michael Phelps is almost done at the U.S. Olympic swimming trials. The superstar has one bit of unfinished business: the 100 butterfly and a showdown with world recordholder Ian Crocker.

Phelps must finish first or second tonight to ensure he swims eight events at the Beijing Olympics. Then he'll need to win them all to surpass Mark Spitz's record of seven gold medals in 1972.

Phelps heads into the final as the fastest qualifier with a time of 51.10 seconds. Crocker, who set the world mark three years ago, was second-best in 51.52.

Those two, along with Georgia swimmer Gil Stovall, were the only men under 52 seconds in the semifinals.

Every time Crocker has beaten Phelps in a 100 fly final, he's set a world record, including against Phelps at the 2004 trials.

"On the days I set records, if you ask me beforehand, I'd say, 'I don't know,'" Crocker said. "It's just one of those things, it happens or it doesn't."

The quiet Texan and the sport's biggest star have been the top two swimmers in the 100 fly since the 2003 world championships in Barcelona, where Crocker set his first individual world record.

"Michael is swimming really well and I'm feeling pretty good, so it should be an interesting race," said Crocker, who was disqualified for a false start in the 100 freestyle preliminaries. "I just want to get on the team."

He needs a top-two finish or the two-time Olympian will go home to his three cats in Austin, Texas.

"He's been waiting all week," Aaron Peirsol said of his training partner.

That's not the case with Phelps, who has four individual victories at the trials, including two world records.

His latest came Friday night in the 200 individual medley. He won in 1 minute, 54.80 seconds, lowering his old time of 1:54.98 set while he won seven events at last year's world championships in Australia.

Spitz, who was at the Qwest Center and presented Phelps with his award, believes the 23-year-old from Baltimore has a good chance to take down the Holy Grail of Olympic records. He came close four years ago, winning six golds and two bronzes at the Athens Games.

"It's time for someone else to take the baton of responsibility," Spitz said. "Thirty-six years is a long time."

Katie Hoff goes for her fifth individual victory Saturday night in the 800 free against Kate Ziegler, a two-time world champion and America's distance queen.

Ziegler has the top qualifying time of 8:29.39, with Hoff second-quickest. Ziegler was runner-up to Hoff in the 400 free.

"The 800 is one of my favorite events. I want to do well," Ziegler said. "It should be a good race. Hopefully, we can push each other to some good times."

As the second-fastest woman ever in the 800 free, Ziegler may challenge Janet Evans' 19-year-old world record in the final.

Elizabeth Beisel, already on the Olympic team at 15, goes for an individual spot in the 200 backstroke final. She qualified fastest in 2:07.78, ahead of Hayley McGregory.

Swimming's most chaotic 22 seconds will be center stage with the men's 50 free.

World champion Ben Wildman-Tobriner qualified fastest for the final in 21.65, ahead of Cullen Jones in 21.71, slower than the American record he set in the prelims.

"I think there's a lot more in the tank," he said.

Also qualifying under 22 seconds were Garrett Weber-Gale, Gary Hall Jr., and Nick Brunelli.

At 33, Hall wants a chance to defend the sprint title he's won at the last two Olympics. He'll be challenged by 32-year-old Jason Lezak.

Those two can take some encouragement from Dara Torres, who's going to her record fifth Olympics at 41 and with a 2-year-old daughter. Torres won the 100 free in 53.78, beating out Natalie Coughlin's 53.83.

"I'm ecstatic. I can't believe it," Torres said.

Overshadowed by Phelps and Torres, Peirsol tied the world record in the 200 backstroke by beating rival Ryan Lochte, who made the Olympic team despite not winning an individual event at trials.

Peirsol shares the world record with Lochte.

"It's weird sharing it, but I have no problems with that," he said.

Another familiar face will be in the pool in China.

Amanda Beard clinched her fourth Olympic berth by finishing second to runaway winner Rebecca Soni in the 200 breaststroke.

"I never get used to this," Beard said. "I'm pumped. This is fun."