Eventually, his 110-meter hurdles heat long over, the former world-record holder and 2004 Olympic champion from China hopped across the finish line, out of the Summer Games without clearing a single barrier for the second time in a row.
Liu stumbled into the first hurdle Tuesday morning, fell to the track and stayed down for a few moments, clutching his lower right leg.
The head of China's track team, Feng Shuyong, later said at a news conference that Liu hadn't been examined by doctors but might have ruptured his Achilles tendon. Asked whether the 29-year-old Liu mentioned retiring, Feng replied: "It is not the time to talk about that."
When Liu — who left the stadium without speaking to reporters — picked himself up off the track, he tried to head to the nearest exit but was pointed back to the race area. So he managed to make his way the length of the race route the only way he could, using his one good leg.
When that slow, awkward trek was complete, another hurdler, Balazs Baji of Hungary, went over and raised Liu's hand in the air, as if to signify he was the winner.
"I respect him. I like him," said Baji, fifth in their heat. "It must be really bad for him. I'm really sorry. I didn't say anything. I just couldn't say anything."
Other competitors went over to offer handshakes of condolences, before Britain's Andrew Turner and Spain's Jackson Quinonez helped Liu into a waiting wheelchair so he could be taken away from the track.
"I wouldn't wish that on my worst enemy," said Turner, who won their heat in 13.42 seconds. "I rate him as one of the best hurdlers we've had in the world ever. I don't like to see that kind of thing."
Four years ago in Beijing, Liu's Olympics ended after two full strides, when he withdrew from his preliminary heat with right foot and hamstring injuries, disappointing his country of more than 1 billion people.
At the 2004 Athens Games, Liu became the first man from China to win an Olympic gold medal in track and field. He backed that up with the 2007 world title, only increasing expectations for another triumph on home soil at Beijing in 2008, one of the main story lines in the lead-up to those Olympics.
He was — and, indeed, still is — China's only track and field superstar, a man whose legs were insured for more than $10 million.
But he's been more than that, too: One of China's most recognizable faces, endorsing shoes and cars and all manner of other products. But in front of a packed Bird's Nest, he never even made it to the first hurdle.
"He had injury for many years, we all know that," Feng said. "But in the last several years, with very good medical care ... it is getting better and better. But still, the injury is still there."
Since winning his Olympic title eight years ago, Liu has not successfully cleared a single Summer Games hurdle.
"For him to push himself and come back ... and for this to happen — it's really sad for any athlete," Usain Bolt said after slowing to a jog and still easily winning his 200-meter qualifying heat Tuesday.
Liu's rivalry with current world-record holder and 2008 Olympic champion Dayron Robles of Cuba was supposed to be a highlight of the London track schedule. Robles advanced easily Tuesday, winning his heat in 13.33 seconds.
What will be remembered about Tuesday morning at the track, of course, was Liu's exit.
"It was just terrible for that to happen to one of the best hurdlers of all time. It was just a tragedy. I hope he's OK," said U.S. hurdler Aries Merritt, who won his heat in 13.07 seconds, the best qualifying time.
"In the hurdles, if you hit a hurdle, to recover is almost impossible. Everyone here is so great — this is the Olympic Games. Everyone here is here to compete. It's just a shame that it had to happen to Liu. I was looking forward to competing against him."
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