LONDON — Rafael Nadal looked hampered by his injured knees during a 6-4, 6-3 loss to Lleyton Hewitt in an exhibition Thursday. He will decide Friday if he can defend his Wimbledon title.

Nadal played without tape on his knees but frequently appeared a step slow on the grass court at Hurlingham Club. This was Nadal's first match since his loss to Robin Soderling in the fourth round of the French Open. He pulled out of last week's grass-court tournament at Queen's Club to rest his knees.

Nadal looked increasingly frustrated against the hard-serving Hewitt, repeatedly failing to get to balls he normally reaches and struggling with unforced backhand errors. He frequently muttered to himself in Spanish after missed shots and often had to rely on his top-spin forehand to escape trouble.

He did not speak to reporters, but uncle and coach Toni Nadal said it was still uncertain whether he can play at Wimbledon, which starts Monday.

Nadal plays another match Friday against Stanislas Wawrinka. Toni Nadal said the top-ranked player will decide after that. When pressed about Wimbledon, the coach did not sound optimistic.

"If it's me, I'm (flying) to Mallorca," he said, referring to the island where Nadal grew up.

Nadal has struggled with knee problems for months and missed last year's Davis Cup final after he was diagnosed with tendinitis in November.

Toni Nadal said his nephew's main problem is bending properly, and wearing some kind of support wouldn't help. He said Nadal has been receiving treatment during his week in London, but "it's not enough."

In the other singles match Thursday at the small private club by the River Thames, Tomas Berdych beat Marat Safin 7-6 (7), 6-4.

Hewitt challenged Nadal from the start, forcing the Spaniard to save two break points in the first game before holding serve. The former top-ranked Australian then managed to break at love for a 3-2 lead after three unforced errors from Nadal. Hewitt held his next service game at love behind a barrage of aces.

Nadal had his first break point in the first game of the second set, but Hewitt saved it with a service winner. Nadal set up another break point at 2-2 with a good forehand volley, but Hewitt made a forehand winner down the line before holding.

Hewitt then broke again for a 4-3 lead after Nadal sent a forehand long, and the Australian converted his second match point after Nadal sent a lunging backhand long.