What Phelps must do for No.7 Friday night

Just got out of a press conference with Michael Phelps here in Beijing, and he explained his strategy for the race that might derail his quest for eight medals -- the 100 butterfly, which will start at 10:10 p.m. Eastern time on Friday.

Phelps has two main competitors in the race: U.S. teammate Ian Crocker and Serbia's Milorad Cavic. Crocker holds the world record (50.40 seconds; expect it to be broken here). Crocker has beaten Phelps three times in the event (but not since 2005). Cavic is not as well known in the States but it sounds like Phelps considers him just as serious of a threat.

The race is up-and-back in the 50-meter pool at Beijing's Water Cube. Phelps wants to go under 24 seconds in his first 50 -- that should take him 16 strokes, he estimates. At that point, Cavic and/or Crocker may be ahead of him. That's OK, Phelps figures, as long as it's not by much.

"I just can't be a body length behind," Phelps said. "When I allow them to get to open water, it makes it harder to fight through the waves."

If Phelps is close after 50, he figures he will win. He's a great closer -- and a great front runner, for that matter. But this is the one that will determine if he has a perfect Olympics or not. Phelps' eighth event -- the 4x100 medley relay on Saturday night (Eastern) -- is almost a given for the U.S.