Phelps Is Facing His Biggest Test

For most of this year's Olympics, Michael Phelps has just had to make sure he didn't mess up.

With the exception of the 4X100 meter freestyle relay, Phelps has come into every event as the clear favorite. But that's not necessarily the case when he faces off against Ian Crocker in the 100-meter butterfly tonight. Phelps has a very clear chance to win the gold, but this is one event where he doesn't hold the world record--Crocker does.

So it should be a very interesting night as Phelps goes to equal Mark Spitz's record of seven gold medals in a single Olympics.

At this point it's almost impossible to bet against Phelps--he's lived up to every expectation, but this should be his toughest test. Crocker is just as good as Phelps in this event, Phelps is not at his best in sprint events (although at this point he doesn't really have any true weaknesses), and unlike the longer distance events, he'll only have one wall. Throughout the Olympics, Phelps has used his ability to rocket out of turns to his advantage, it won't be nearly as much of an advantage tonight.

And he doesn't just have Crocker to worry about. Former Olympian Gary Hall Jr. says that Phelps will need to keep an eye on Serbian Milorad Cavic as well.