Michael Phelps, shockingly shut out of the medals in the 400m medley, will try to bounce back in an event he has long dominated when he launches his Olympic 200m butterfly title defense tomorrow.

Ryan Lochte, for one, thinks Phelps will come back with a vengeance.

"The next event he is in, he is going to light it up," Lochte predicted after claiming gold in the 400m medley as Phelps floundered to fourth.

Phelps couldn't ask for a better forum in which to reassert himself.

He burst onto the international scene as a 15-year-old with his second-place finish in the 200m fly at the 2000 Olympic trials, displaying the stunning closing ability that has become a trademark.

He has held the world record for more than a decade and been untouchable in international competition.

He owns the four fastest times in history, and his world record of 1min 51.51sec is more than one second faster than the second-best performer in history, Hungarian Laszlo Cseh at 1:52.70.

Even when his goggles filled with water, leaving him virtually blind in the final in Beijing, Phelps held on to beat Cseh for one of his historic eight gold medals.

There's no question the world has been gaining on him. China's Wu Peng beat Phelps twice in the 200m fly at grand prix meets in the States this year, although he can expect to face a different Phelps in Olympic waters.

Wu is the fourth-fastest swimmer in the world this year in the event behind Phelps, Japan's Takeshi Matsuda and controversial Australian Nick D'Arcy.

D'Arcy's coach Michael Bohl acknowledged that Phelps "is the runaway favorite" to claim a third straight Olympic title in the event.

Phelps' team-mate Tyler Clary added a little intrigue to the race with some highly publicized comments questioning Phelps' work ethic.

Phelps said Clary had apologized and the two had cleared the air, but added ominously that he preferred to express his feelings "in action".

That bodes ill for Clary, who was already swimming upstream in an event in which he has never earned a medal in a major international competition.

Phelps, whose opening day struggles at the Aquatics Centre started with a lowly eighth-fastest time in the medley heats, said he'd just try to put it behind him.

"The biggest thing now is to try and get past this and move forward," he said. "I have a bunch of races and hopefully we can finish this a lot better than we started."