ROME  Michael Phelps had stayed all but mum on the suit controversy that's rocked swimming and rewritten the record book at this week's world championships. But in the 100-meter butterfly final Saturday, he shook off a head-to-head collision an hour earlier in the warm-up pool to make the loudest statement of all.

Phelps, as at last year's Beijing Olympics, once again overpowered Serbian speedster Milorad Cavic in the last few meters to post a come-from-behind victory. After winning in a world-record 49.82 seconds, Phelps pounded his fists on the water and pulled at the suit on his chest to make an emphatic point.

"It doesn't matter what suit you wear," he said afterward. "It matters how you train."

Cavic was wearing the Arena X-Glide, one of the all-polyurethane suits that, for some swimmers, appear to reduce friction and enhance buoyancy to help them swim significantly faster. Out of loyalty to longtime sponsor Speedo, Phelps was wearing last year's LZR Racer, which, with polyurethane panels, is the first generation of the new suits.

Phelps has set two world records in the LZR this week but also suffered a shockingly lopsided loss to Germany's Paul Biedermann in the 200-meter freestyle. Biedermann also wears an Arena X-Glide.

Earlier this week, Cavic said that "people, if I were to beat Phelps, they would say, 'Cavic beat Phelps because of the suit.' " The day before the race, he told reporters he would buy Phelps one of the new suits if Phelps wanted one. Phelps declined.

Instead, Phelps swam a near-perfect race Saturday, covering the first 50 meters faster than he ever has, in 23.36 seconds. Cavic, a faster starter than Phelps, did it in 22.69 seconds.

Phelps reeled in Cavic with his trademark closing speed. In Beijing, he edged Cavic by a mere 1/100th of a second. This time, the finish was much more decisive, with Cavic finishing second in 49.95 seconds.

"It definitely gives a little extra motivation when there are comments," Phelps said. "That's just part of sport. I think it makes it more exciting."

Cavic noted that he "never attacked Michael" with his pre-race comments.

"I have nothing but respect for Michael," Cavic said. "He is the best. Do I have regrets? I don't see that I did anything wrong."

Phelps and Cavic became the only two swimmers to finish the 100 fly under 50 seconds.

"It was an incredible race," Cavic said. "We all went a lot faster than we expected."

Phelps didn't know what to expect this season after taking six months off from training after the Beijing Olympics, where he won an historic eight gold medals. His subpar preparation has showed at worlds, in his relatively slow relay swims and especially in his loss to Biedermann.

But on Saturday, he delivered what his coach, Bob Bowman, called his "best, by far" race in the 100 fly. That's high praise, considering last year's finish in Beijing and the multiple by-a-fingernail battles he had with American Ian Crocker in the event.

"You can tell after my celebration that it satisfied me a little bit," Phelps said.

An hour before the race, Phelps was sharing a lane with Australian Cate Campbell in the warm-up pool. The two were too close when Phelps broke into a butterfly sprint, and they collided heads. The force broke the nose bridge on his goggles and tweaked his left shoulder.

Bowman, watching from the pool deck, shouted "No!"

Phelps initially had blurry vision in his left eye.

"I tried to really just get that out of my head," he said of the collison. "It kind of took us by surprise. It kind of shocked me, took the wind out of me a little bit."

Campbell said she "laughed it off" and proceeded to break a championship record to qualify first in the semifinals of the 50-meter freestyle. (American Dara Torres qualified eighth for the Sunday final.)

Phelps proceeded to swim a race that got him more pumped up than he's ever been.

"I have not ever seen him that emotional and he deserved it," Bowman said. "That was a tremendous race."

Phelps has one event left — the 400 medley relay Sunday night, assuming the U.S. doesn't mess up in the morning prelims. The Americans will be a heavy favorite in that one as well.

Three other world records were set Saturday, bringing the total to 39 with one day left at the final meet for high-tech bodysuits.

Kirsty Coventry of Zimbabwe took down her down mark in the 200 backstroke, winning in 2 minutes, 4.81 seconds. Russia's Anastasia Zueva also went under Coventry's old mark of 2:05.24, but her 2:04.94 was only good enough for the silver. American Elizabeth Beisel claimed bronze.

China claimed the record in the women's 400-meter medley relay. Li Zhesi finished it off in 3:52.19 to beat the mark set by Australia (3:52.69) at the Beijing Olympics. The Aussies also went under the old mark, settling for silver in 3:52.58. Germany took the bronze.

The winning team also included Zhao Jing, Chen Huijia and Jiao Liuyang.

In a semifinal heat of a non-Olympic event, Britain's Liam Tancock set a world record of 24.08 in the 50 backstroke, eclipsing the mark of 24.33 held by American Randall Bal. Junya Koga of Japan also went under the previous record time to win the second heat at 24.29. The final is Sunday night.

Cesar Cielo of Brazil completed a sweep of the freestyle sprints with the 50-meter title. Cielo added to his title in the 100 with a one-lap time of 21.08 to hold off world-record holder Fred Bousquet (21.21) and fellow Frenchman Amaury Leveaux (21.25).

Managing to win world titles without world records: Australia's Marieke Guehrer in the women's 50 fly and Lotte Friis of Denmark in women's 800 freestyle. Olympic champion and 800 world-record holder Rebecca Adlington finished fourth.

Contributing: Wire reports