EUGENE, Oregon (AFP) - World champion Tyson Gay suffered a left hamstring strain in his collapse at the US Olympic Track and Field Trials and will not resume top-speed training for two weeks, his manager said Sunday.

Mark Wetmore, agent for the US sprint star, also said Gay will run in London on July 25 as planned and indicated that the injury would not keep him from next month's showdown with Usain Bolt and Asafa Powell at the Beijing Olympics.

Wetmore updated Gay's condition after an MRI late Saturday, hours after Gay's bid for a golden double in the 100 and 200 meters ended in pain when he fell 12 steps into a 200 quarter-final heat with what had been called a cramp.

The exam showed Gay has a mild strain in the semitendinosus muscle, one of the hamstrings, and will be forced to slowly work his way back to a full-speed workout regimen ahead of the Beijing Olympics.

Gay plans to engage in "active rest" for 12 to 14 days, according to his manager, with increased light physical activity over the next two weeks leading to a resumption of full training.

That should put Gay back on his routine five days before his only planned Beijing 100 tuneup in England.

"Tyson's only confirmed pre-Olympic competition is the 100 meters at the London Grand Prix on July 25 and that is still on the schedule," Wetmore said.

Gay turns 26 on August 9, the day after the opening ceremonies of the Beijing Olympics and six days before the opening round of the 100 at Beijing.

Gay booked a Beijing berth last Sunday by winning the 100 in a wind-aided 9.68 seconds, the fastest 100 ever run under any conditions, but his fall in the 200 doomed his dream of matching his double from the 2007 worlds at Osaka.

"I'm very disappointed," Gay said. "It's just one of those things."

For many tense minutes, it looked like a hamstring pull that would have kept Gay from Beijing altogether.

"I'm really glad it was a cramp as opposed to what it looked like," said women's 100 Olympic qualifier Lauryn Williams. "My eyes started to well up. I was like, 'Please God, don't take him away from us now. The USA needs him.'"

Jamaica's Bolt set the world record of 9.72 on May 31 at New York, beating Gay and breaking the old mark of 9.74 held by compatriot Powell.

A showdown among the three to decide who is the world's fastest man is expected to be among the signature moments of the Beijing Olympics, but the setback for Gay is certain to spark talk of whether he can regain top form.

"I hope he heals quick," said US 100 rival Walter Dix.

Bolt plans to run the 100 and 200 in Beijing while Powell and Gay will only run the 100.

Jon Drummond, Gay's coach, said that every precaution was taken with his star pupil after last week's amazing 100 run but admitted that unprecedented speed marks put recovery efforts into uncharted territory.

"All the things that we know to do, we did," Drummond said. "The reality is he ran 9.6 in the 100 and wind-aided or not, the body still produced that type of velocity. We don't really know what that type of running does to the body.

"We know now and we can go back and study the science after this meet. We've got to accept whatever right now. He seemed very positive. He didn't strike me as broken-hearted, but I'm sure there is disappointment."

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