ATHENS, Ga. -- Michael Phelps powered to the wall and quickly searched for the scoreboard.

He liked what he saw.

Phelps turned in perhaps the most impressive performance so far in his comeback, posting the third-fastest time in the world this year while easily beating rival Ryan Lochte in the 100-metre butterfly at the Bulldog Grand Slam on Friday night.

Despite some problems with his turn, Phelps had the packed house roaring when he touched in 51.67 seconds, considerably faster than the 52.11 he posted at the Santa Clara Grand Prix three weeks ago.

Lochte was a distant second in 53.08.

"I wanted to get under 52," Phelps said, breaking into a big smile. "I was sick and tired of seeing 52.1."

He had no trouble finishing ahead of Lochte, though it really wasn't a fair fight. Phelps' longtime foe also swam the 200 freestyle, winning the "B" final less than an hour before he returned to the water to face a rested Phelps.

More important for Lochte -- his left knee seemed to hold up well.

This is his first meet for the laid-back Floridian since he reinjured the surgically repaired knee at the Mesa Grand Prix in April. It was initially hurt late last year when he tried to catch an exuberant fan and fell into a curb, requiring surgery.

"I hope I lose," said Lochte, who plans to swim a grueling six events in Athens. "It will just make me more hungry."

Phelps is set to swim three events at the weekend meet on the University of Georgia campus, a hastily arranged event that gave some of the top swimmers on the East Coast a chance to swim one more time competitively before the next month's national championships in Irvine, California.

The results from nationals, as well as the Pan Pacific Championships being held in Australia later in August, will determine the U.S. team for the 2015 world championships.

Phelps seems to be right on course, at least in his signature fly, finishing just 0.46 off the time that won the gold at the 2012 London Olympics. The only faster times this year were Thomas Dal's 51.44 in the Belgian Open and Viacheslav Prudnikov's 51.60 at the Russian national championships.

"I am very pleased with being able to go 51," Phelps said. "But in the grand scheme of things, I think it's just a small steppingstone to go where we hope to be."

He is still struggling with the consistency of his stroke. When things are going well, Phelps needs 16 strokes to cover the first 50 metres, 18 for the return lap. When he's just a little off, he winds up gliding into the wall too much, either when he's making a flip turn or coming to the finish.

"I was kind of bummed that I still can't hit a wall correctly," Phelps said.

Added his coach, Bob Bowman, "He looked crazy coming off the wall."

All in all, though, no complaints.

Phelps, who retired after the last Olympics and stayed away from the pool for more than a year, didn't come back to tarnish his legacy, which includes 18 golds and 22 medals overall -- far more than any other Olympic athlete.

"I always set high expectations for myself, no matter what I'm doing," he said. "Bob and I have a plan of what I want to do. He knows what it's going to take to get there."