Olympic decathlon champion Bryan Clay withdrew from the U.S. national track championships Thursday with an injured left hamstring, a decision that could force him to shut down his entire 2009 season.

Clay, who hurt himself Tuesday in workouts, warmed up briefly before the meet started, but decided he couldn't compete.

Because of that, he can't qualify for the world championships, to be held in Berlin later this summer. Only the top three finishers this week at nationals receive bids, and Clay's Olympic gold medal doesn't earn him a wild-card spot.

"I've got to sit down with my coaches, my agents and weigh the options," said Clay, who will spend the rest of the week tweeting about nationals. "I've got to see where we're at, see what meets are out there. I honestly don't even know where to begin for that."

Clay said the injury would probably be healed in six or seven days. But he was still within 48 hours of hurting it, and extensive time in therapy over the last two days wasn't enough to get him in competition form.

"If I could go out there and run a 10.8, I'd run a 10.8 in the first event, the 100," Clay said. "But there's no way I can run a 10.8 today, so we shut it down. There's no use in me going out there, running an 11.5, risking further injury and maybe not be able to finish anyway."

The decision to withdraw not only hurts Clay, it also deprives the sport of one of its biggest stars in a marquee event. And it brings one of track's strange rules back to the fore. Titlists from the last world championship, in 2007, receive automatic bids into the 2009 championships but 2008 Olympic champions do not.

Meanwhile, American rules call for the top three finishers _ along with defending world champions _ to earn spots at worlds, with no exceptions for injuries.

That has led to a strange program this week, with runners like Tyson Gay, Jeremy Wariner and Bernard Lagat, none of whom won Olympic gold, able to skip marquee races because of their 2007 titles while Clay gets no such break.

"The rule doesn't bother me at all," Clay said. "I just wish the Olympic champions were included in on that rule for the year after the Olympics. I can honestly say if that rule was the same for Olympic champions, I know in my heart I'd be going to world championships ready to compete for a medal in six weeks."

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MEMORABLE MARK: The scar on 800-meter runner Christian Smith's left shoulder is fading faster than he wants.

The memory of that mark, though, never will.

Smith dove across the finish line last summer at the Olympic trials in Eugene, edging out Khadevis Robinson for the last spot on the U.S. squad bound for Beijing.

The tumble took its toll, as Smith wound up bloody and bruised, unable to practice for a week.

Know what?

He'd do the same thing again.

"People still ask me about it," said Smith, who spends part of the year training in Eugene. "It was exciting."

Smith didn't need a dive to win the preliminaries on Thursday night, finishing with the fastest time.

"I was pretty anxious going into today," Smith said. "Getting done with the first round is always good to do."

Smith's plunge last summer was part of an even bigger drama that day, as he, Nick Symmonds and Andrew Wheating _ all fan favorites with heavy ties to Eugene _ sparked the biggest celebration with a 1-2-3 finish.

Symmonds also advanced in the 800 on Thursday, while Wheating tried out the 1,500 but pulled out before the race with a slight tear in his calf.

The three buddies commemorated making the U.S. team soon after Beijing, getting the Olympic rings tattooed on their right shoulders.

"It was fun for all of us to get the same thing," Smith said.

Still, Smith wishes the scar would stick around.

It goes so well with his story.

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HASAY'S EXIT: Jordan Hasay electrified the Hayward Field crowd last summer at Olympic trials, fans chanting her name as she circled the track, her trademark long, blond ponytail bobbing behind her.

Hasay made quite a run, too, advancing to the finals in the 1,500 before finishing 10th and missing out on a trip to Beijing.

However, she broke the national high school mark with a time of 4 minutes, 14.50 seconds during her amazing run.

This summer, things didn't go quite as well. Her training was interrupted by a severe sinus infection, the 17-year-old was eliminated in the first round.

"I'm disappointed," she said. "I didn't have the acceleration ... My fitness is not as well as I'd like."

Hasay, who is from Arroyo Grande, Calif., will soon be in Eugene on a regular basis, after deciding to run with the Ducks this fall.

"I'm really excited," she said.

Her championships may not be done just yet. Hasay is keeping the door open to running in the junior version of the 1,500 on Saturday.

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AP Sports Writer Pat Graham contributed to this report.

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