'I got nothing left,' Phelps recalls saying

The "60 Minutes" interview with Michael Phelps airs tonight after the completion of CBS' NFL coverage.

NEW YORK - After winning his sixth gold medal of the Beijing Olympics, Michael Phelps feared he wouldn't be strong enough to win his seventh.

But a mistake by rival Milorad Cavic enabled Phelps to pull out an improbable victory in the 100-meter butterfly.

Phelps, who went on to break Mark Spitz's record by winning eight golds in China, discussed his performance in an interview with the CBS news show "60 Minutes," to be broadcast tonight.

After winning the 200 individual medley, Phelps expressed his fears to coach Bob Bowman.

"I got nothing left," he remembered saying to Bowman, according to an excerpt of the interview released by the network.

Bowman saw it, too.

"If you look at the pictures right after the [200 IM] and even when I was standing there and he was in the water, I thought, 'Wow, he is really tired right now,'" Bowman told "60 Minutes."

In the fly, Cavic was clearly ahead as the two swimmers approached the wall. The Serbian glided to the finish with his arms outstretched, while Phelps took an extra half-stroke that gave him the victory by one-hundredth of a second -- the smallest possible margin.

Phelps pointed to a subtle but crucial mistake by Cavic.

"He's picking up his head, so it's acting like a speed bump," Phelps said, pointing to a picture of the finish. "So he's coming up and then trying to lift his head before he touches the wall. ... [Phelps' head] is in a straight streamline. So that's the difference in the race. If his head is down, he wins, hands down wins the race."

After beating Cavic, Phelps teamed with three other Americans the following day and won the 400 medley relay, breaking Spitz's record of seven gold medals at the 1972 Munich Games.

Phelps said he plans to resume training in January to begin preparing for next summer's world championships in Rome. He also intends to compete in the 2012 London Olympics and has not ruled out making another run at eight gold medals.

ASSOCIATED PRESS