Charlton's China international Zheng Zhi has a back injury and is a major doubt for next month's Olympics.

The midfielder was carrying the injury throughout the latter stages of China's unsuccessful World Cup qualification run and is struggling in his bid to represent the host nation in Shenyang, one of five cities hosting the tournament.

China's Olympic football coach Ratomir Dujkovic believes Zheng's absence would be a blow.

"Zheng Zhi is China's best player," Dujkovic said. "If he can't play for the Olympic side, it will be a severe loss for China.

"If he were not in form, it would be pointless for me to include him in the Olympic squad.

"I hope he could recover and I won't make a decision to drop him until the last minute."