London - Rafael Nadal's chances of defending his Wimbledon title were looking grim Thursday after the world number one was beaten 6-4, 6-3 in an exhibition match by Lleyton Hewitt.

Nadal, who lost to Robin Soderling at the French Open due in part to tendinitis in his right knee, appeared to be far from his best on the grass at Hurlingham club at the unofficial pre-Wimbledon tune-up.

The Spaniard who put in three hours on the practice court upon arrival in London on Tuesday, appeared to be in some discomfort, having trouble going low for shots, a key requirement on the lawns.

"Rafa is having trouble bending his his knees," his coach and uncle Toni Nadal said. "We must to wait and see."

Nadal will hope to make an improvement when he plays another exhibition match against Swiss Stan Wawrinka Friday. The Wimbledon top seed played Hewitt for nearly
90 minutes without any protective strapping on his knee.(dpa)