EUGENE, Ore. — Sprinter Tyson Gay has a mild strain in a muscle in the back of his left leg but says he'll be 100 percent for his two races at the Beijing Olympics.

Gay has been told to restrict himself to light physical activity for the next two weeks. He pulled up abruptly in the first 40 meters of his 200-meter qualifying race Saturday at the U.S. Olympic track and field trials and had to be carted off the track.

He was diagnosed with a severe cramp in his hamstring, and an MRI that afternoon revealed the strain.

"I'll be 100 percent for the 100 and 400 relay," Gay said in an NBC interview before Sunday's 200 final.

Gay said he felt a "little tweak" in the hamstring before the race and told coach Jon Drummond, who recommended he not run. But Gay didn't take that advice.

"I thought it would go away once I warmed up," he said. "By the time I came off the blocks, 20, 25 meters into the race, my hamstring pulled up."

A statement from his representatives said he is "expected to engage in 'active rest' for up to 12-14 days, with light physical activity increasing through that period, then resume training."

Gay said doctors told him it could be as short as one week.

The only meet he's signed up for before the Olympics is the 100 meters at the London Grand Prix on July 24-25.

Gay, the defending world champion in the 100 and 200, already has qualified for the Olympic 100 meters. That competition begins Aug. 15 in Beijing. If he can run, he also would be expected to be part of the 400-meter relay team.

"I was upset," Gay said, "but then again I was still thankful it didn't happen in the 100 and I still have the chance to go to the Olympics."

Bubba Thornton, head coach of the U.S. men's team, said he saw Gay on Sunday morning.

"He has an injury, and I'm very confident that he's going to be in place when they say 'On your mark'" in Beijing, Thornton said.

He wouldn't get specific when asked what kind of readiness Gay must show to be included on the relay team.

Regardless, Gay's shot at a 200 medal is gone. USA Track and Field rules state only the top three finishers qualify for the Olympics, regardless of a runner's past record or any injuries.

The concept behind the selection process has become a topic of debate since Gay's injury.

"I'm very comfortable with the rules," Gay said. "I understand it's been like this for years. That's the way it goes."

In other sports, there is room for injury petitions. For instance, in gymnastics, defending all-around gold medalist Paul Hamm broke a bone in his hand in the first round of nationals, an injury that forced him to drop out of that event and miss Olympic trials. However, he was placed on the team provided he shows he's ready at a training camp in two weeks.

There is no such process in track, even though in Gay's case it could cost the United States a gold medal. USATF does it that way to avoid politics and other subjective criteria.

"What you'd end up having is athletes perhaps in other events feigning injuries to gain access," USATF president Bill Roe said. "So you can't really take injury into account. I don't think that's one of the criteria we'd use in any case."