World number one Rafael Nadal will decide on Friday whether to defend his Wimbledon men's singles crown.

Rafael Nadal, plagued by knee problems, struggled with his general movement during an exhibition match in London on Thursday. Nadal went on to lose 6-4 6-3 to Lleyton Hewitt.

"Today's match was a real test, as close to reality as it could get," said Nadal after his loss.

"I will come back and play again and then make my decision about playing at Wimbledon or not."

Nadal will play Switzerland's Stanislas Wawrinka on Friday, following which he is scheduled to hold a press conference and will announce his decision.

Rafael Nadal's participation at Wimbledon, which starts on Monday, is looking increasingly doubtful.

"He is having difficulties bending and it seems his treatments aren't enough, I don't know if he will defend his title, we have to wait for Friday." said coach and uncle Toni Nadal.

Nadal was forced to withdraw from last week's tournament at Queen's Club with knee trouble and underwent intense rehabilitation in Barcelona.

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