With a defiant performance in a supposedly inferior suit, Phelps stayed close over the outward lap and rallied on the return to become the first swimmer to break 50 seconds in the 100-meter butterfly, beating the Serbian with a time of 49.82.
Cavic also broke 50 seconds, but 49.95 was only good enough for silver. He wasn't nearly as close as last year's Beijing Olympics, when Phelps famously won by one-hundredth of a second and Cavic always maintained that he actually touched first.
When Phelps saw his time at the Foro Italico, he hopped up on the lane rope separating him and Cavic, threw up his arms and let out a scream toward the U.S. cheering section.
Showing as much emotion as he ever has, Phelps also slapped the water and tugged at his Speedo LZR Racer swimsuit — no doubt in reference to Cavic offering to get Phelps one of those supposedly faster polyurethane suits so he wouldn't have any excuses.
No need, Milorad.
Phelps did just fine with what he had.
"How can it not motivate you? When there are things that are said, the only thing it does for me is fire me up," Phelps told NBC. "It does nothing but literally motivate me to no end, and I love it."
The two rivals finally shook hands, but that was about it.
Nothing more needed to be said.
"This is just a testament to Michael Phelps," Cavic said. "He can do it all."
Cavic did say one thing to Phelps: "You're the man."
"He just looked at me and smiled," Cavic said. "He knows it."
In one of the most memorable events of the Beijing Olympics, Phelps pulled out an improbable victory on his final half-stroke to beat Cavic by the narrowest possible margin. Without that win, Phelps would not have broken Mark Spitz's record with eight gold medals in a single games.
Cavic has stewed over the loss ever since, believing he touched first but didn't put as much pressure on the touchpad as Phelps, who ad-libbed a final half-stroke and crashed into the wall much harder. Even though all electronic and photographic evidence shows Phelps won, Cavic repeated his claims when he got to Rome.
He also tried to get into Phelps' head, saying it was the American's own fault for sticking with a Speedo suit that isn't as fast as polyurethane models such as the Arena X-Glide, which Cavic wears.
The Serbian offered to get Phelps an X-Glide "within the hour," or buy him another of the rubberized suits out of his own pocket. Cavic said he would really prefer to race Phelps wearing nothing but briefs, so everyone would know who the best man is without any help from the suits.
Phelps said he would do his talking in the pool.
That's just what he did Saturday night, setting the 37th world record of the fastest meet in history and getting back the mark Cavic snatched away a night earlier with a time of 51.01 in the semifinals.