Michael Phelps at U.S. Olympic Swimming Trials

One down, seven to go for swimming star Michael Phelps.

But it wasn't an easy one.

In his first of what is expected to be eight finals at the Olympic swimming trials, Phelps set a world record in the 400-meter individual medley Sunday night. And it's a good thing he did because otherwise he would have lost to Ryan Lochte, who also dipped under Phelps' old mark of 4:06.22.

Lochte was only .02 behind Phelps heading into the final stroke, the freestyle. But Phelps pulled away, finishing with a time of 4:05.25, .83 ahead of Lochte.

Phelps became the first person to dip into the 4:05s. Four years ago Phelps set a record of 4:08.41. So how low can the record in this event go?

His coach Bob Bowman wouldn't predict a time, but said he expects Phelps can shave a bit more off the mark.

So here's a prediction. If Lochte is swimming well enough in Beijing to challenge, look for Phelps to become the first person to get into the 4:04s.

Someday - maybe not in the too distant future - swim fans will see the first sub-4:00 400 IM.