AP photo

All eyes will be on Michael Phelps as he goes for another gold medal in the 100-meter butterfly, but the real man to watch in this one might be Phelps’ teammate, Ian Crocker, who holds the world record in the event, 50.40 seconds.

This might be Phelps’ toughest test of the Games. He has the fastest time in the world this year, at 50.89 seconds, and beat Crocker in the Olympic Trials, the 2007 World Championships and the 2004 Olympics in Athens. But all those races were tight.

Could this be Crocker’s moment?

The race is scheduled for 10:10 p.m. EDT Friday, and will be shown live on NBC.

— Mike Persinger