BEIJING — Liu Xiang's coach is doubtful the former Olympic champion hurdler will ever run as fast as he once did, and Liu himself says he'll retire if he gets injured again.

The 2004 Olympic champion underwent surgery on his right foot in December in Houston, Texas. The injury kept him from defending his 110-meter hurdles title at last summer's Beijing Games, where he was the country's best hope to win gold in athletics.

"He (Liu) was a top-level athlete before the injury, but now his training has been badly affected and it will be difficult to run those best times again," his coach, Sun Haiping, was quoted Thursday in the state-run English-language China Daily.

"I'm afraid even if he is fit physically, he will be distracted by the fear of getting injured again."

Liu, 25, is a former world record holder and defending world champion. He established his world record of 12.88 seconds in 2005. His record was surpassed on June 12 by Cuban Dayron Robles (12.87), who also won gold in Beijing.

"If I get injured again I will say goodbye to the sport," Liu told the newspaper. "Even if I had not suffered this injury, I planned on retiring around 30."

Liu's coach has said he will compete in the world championships in August in Berlin if he's able to run the 110-meter hurdles in under 13.20 seconds.