Why wouldn’t they disclose the injury?

Defending champion Rafael Nadal pulled out of the London Olympics on Thursday with an undisclosed injury, leaving the tennis competition without one of its leading stars and robbing Spain’s team of its flag bearer for the opening ceremony.

Nadal won the French Open for a record seventh time this year but has struggled with left knee problems at times during the season. Shortly after winning his 11th Grand Slam title at Roland Garros, he lost to 100th-ranked Lukas Rosol in the second round at Wimbledon.

Nadal has not played since.