It took Tyson Gay only 9.75 seconds to prove that, yes, he's healthy, and leave the rest of the world wondering what he might do next.

With a helping wind at his back, America's best-known sprinter ran the 100 in the seventh-fastest time under any conditions Thursday, then exited stage right, not to be seen again at the U.S. championships.

About a half hour after he ran, Gay's coaches confirmed he wouldn't be racing again this week.

"But I want to," Gay said. "Because I ran a horrible race."

Probably not what the competition wants to hear.

Already qualified for this summer's world championships in Berlin, Gay used this single race at nationals as a tune up. Because of the wind, the 9.75 won't go down as the new American record, even though this was .02 seconds faster than the mark he set last year on the same track.

Record or no, over the past four weeks, Gay has made his point: He's ready to take on world-record holder Usain Bolt.

Combine this with the 19.58 he clocked in the 200 in May in New York _ only the third sub-19.6 ever in that event _ and it's clear Gay is over whatever ailed him last year when an injury in the 200 at Olympic trials, also on the same track in Eugene, derailed his season.

Was he trying to send a message?

"Not necessarily to anybody in particular, but more for myself," he said. "I knew it was wind-aided, so of course it doesn't go into the books. But at the same time, it still lets me know that my legs are ready to turn over faster. They're a lot faster when I execute the beginning part."

Gay's eye-opening time came despite a bad start and stood as the biggest _ or maybe the best _ news on the first day of nationals, which lost a star before they even began when Olympic decathlon champion Bryan Clay withdrew with an injury.

Before Gay's run, the women took to the track and everything went to form, with Allyson Felix, Muna Lee, Lauryn Williams, Carmelita Jeter and Torri Edwards all advancing to Friday's semifinals.

Olympic champion LaShawn Merritt cruised to a win in 45.23 seconds in his prelim, which was missing Jeremy Wariner, who also has a bye into worlds. Wariner will run in the 200 later this week.

Sanya Richards (400) and Lopez Lomong and Alan Webb (1,500) were among the other big names who advanced easily.

Bernard Lagat, the 2007 champion in the 1,500 and 5,000, ran a qualifying heat in the 800 but, like Gay, was using this only for training work and won't run again this week.

Gay will leave Eugene with a 9.75-second body of work that included that bad start. Moments before the race started, a false start left everyone in the field one flinch away from being disqualified.

"So I had too much going through my mind, instead of worrying about execution," he said. "When I got out of the blocks, I felt sloppy, felt someone beside me. I think it was Leroy Dixon, who was winning until about 60. Then I caught up with the field and tried to run relaxed through the finish line."

Gay beat Dixon by .25 seconds and second-place finisher Monzavous Edwards by .23.

The 2007 world champion said if it had been up to him, he'd race again this week. But there are coaches and agents and schedules to keep, and it appears his team was satisfied with simply seeing him get the cobwebs out.

The semifinals should still offer some drama, though. Olympic medalists Shawn Crawford and Walter Dix and 60-meter indoor champion Michael Rodgers all moved onto Friday with ease.

They're all vying for a national championship.

Tyson Gay was seeking something else.

"Phenomenal. He always looks phenomenal," Crawford said. "If he steps on the track, he's ready. That's a given. We know that. Running 19.5, you can't expect anything less than that."