LONDON — Chad le Clos still has Michael Phelps' number.

Le Clos was the fastest qualifier in the 100-meter butterfly preliminaries at the London Olympics on Thursday, with Phelps second after rallying from last at the turn.

Le Clos outtouched Phelps to win the 200 fly on Tuesday, when Phelps became the most decorated Olympian ever. The American came back after silver in the 200 to help the U.S. win the 4x200 free relay and earn his 19th career medal.

Le Clos won his 100 heat in 51.54 seconds, while Phelps took his heat in 51.72 as he tries to become the first male swimmer to win the same event in three consecutive Olympics. Phelps was last coming off the 50-meter wall before gradually picking off everyone in the field to touch first.

Milorad Cavic, the U.S.-born Serb who lost the 100 fly to Phelps by a hundredth of a second four years ago in Beijing, was fifth-fastest in 51.90.

Also moving on to the evening semifinals was Tyler McGill of the U.S., seventh in 51.95.

George Bovell of Trinidad and Tobago qualified fastest in the 50 free, with defending champion Cesar Cielo of Brazil right behind.

Bovell touched in 21.77 seconds to win the sixth of eight heats in swimming's glamour event. The 29-year-old four-time Olympian is solely focused on the 50 at these games after winning his country's first swimming medal at the 2004 Athens Olympics in the 200 individual medley. The former Auburn swimmer once owned the 200 IM world record.

Cielo finished the furious one-lap sprint in 21.80, with teammate Bruno Fratus third at 21.82. Cielo had a quick turnaround after finishing sixth in the 100 free a night earlier.

"It was hard to sleep last night after the race because the final was so late," Cielo said. "This morning I was more concerned about making enough of an effort to get back. It's a matter of resting now to make sure I get a spot in the final."

Anthony Ervin of the U.S. was fourth at 21.83 in his return to the Olympics after a 12-year absence. He tied American Gary Hall Jr. for the gold at the 2000 Sydney Games before leaving the sport. He traveled, promoted concerts, played guitar in a band and taught swimming lessons to pay his bills. He sold his gold for $17,100 to help victims of the Indian Ocean tsunami.

"I definitely had some first-race jitters," Ervin said. "It didn't feel like that was everything coming together, so hopefully I can make that happen in the next two swims."

He still had his warmups on when his rivals had taken theirs off and were waiting behind the blocks.

"I felt like I was a little rushed," Ervin said. "When they blew the whistle I was still taking off my shoes. I was like, 'Ahhhh.' Twelve years ago was a long time ago. Maybe it's the same kind of venue, working within the same kind of institution, but I have grown a lot over the last 12 years."

Ervin trains at California with 100 free champion Nathan Adrian, who out-touched James "The Missile" Magnussen of Australia for the gold on Wednesday. Adrian didn't qualify for the 50 at the U.S. trials.

"Nathan just dug in. He was like 'Uhhh!'" Ervin said. "He just wanted it. He fought for it in that last stroke. He took it."

Magnussen, who settled for silver, moved on to the evening semifinals in 10th at 22.11 after a sleepless night thinking about how close he came to winning Australia's first swimming gold of these games.

"The last thing I wanted to do was to get up and swim again," he said. "I don't think I've really had the chance to come to grips with it yet."

Teammate Eamon Sullivan, the 2008 silver medalist in the 100 free, claimed the 16th and last spot for the semis.

"I just lost it on the start, which is probably the most crucial part of the race in the 50," he said. "I've been swimming great in the warmup so I was expecting to go faster than that."

Brent Hayden, who won Canada's first medal in the 100 free with a bronze, was 13th-quickest in the 50.

Roland Schoeman of South Africa, the 2004 bronze medalist in the 50, qualified fifth at 21.91. The 32-year-old sprinter was the oldest of the 16 semifinalists.

Cullen Jones of the U.S. also moved on. He was sixth at 21.95 in pursuit of his first individual Olympic medal after failing to make the 100 free final.

"I hate swimming in the morning, but I'm going to be ready for tonight," he said.