VINA DEL MAR, Chile - Rafael Nadal's ailing left knee may continue to bother him until the end of the month, his coach said Monday.

Nadal practiced for 90 minutes with Nicolas Massu of Chile on Monday, his fourth straight day of training since arriving in the country for his first match in more than seven months.

Nadal opens play on Tuesday in the VTR Open, playing doubles with Argentina's Juan Monaco. On Wednesday, he will play singles in the second round against the winner of a first-round match between Argentines Guido Pella and Federico Delbonis.

"The knee is much better, but they've told us he will feel some discomfort and lack of mobility until the end of the month," said Toni Nadal, the seven-time French Open champion's coach and uncle. "But it's definitely getting better."

Nadal has avoided surgery so far, getting therapeutic treatment in hopes of speeding the healing. But the slow recovery from the inflamed knee means Nadal has been trying to lower expectations as he uses three Latin American clay-court tournaments to prepare for a run at an eighth French Open title.

Nadal has practiced in Chile wearing a white bandage around his knee.

"The bandage is normal and is part of the treatment," his coach said.

Nadal will be watched closely in doubles on Tuesday, which is meant to give him extra playing time on top of his matches in singles.

His uncle has called the small Chilean tournament "our first French Open."

Nadal has the best clay-court record in the Open Era, winning 93 per cent of his matches. Many will expect him to sweep through this event as he would in the first week of the French Open, perhaps without dropping a set. Anything less will add to speculation about his future and could add pressure.

"His game is much better than when we got here," Toni Nadal said. "It was better yesterday and even better today. We're looking to the doubles as an added test."

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