WASHINGTON — Gilbert Arenas had a third operation on his bothersome left knee this morning, once again throwing into doubt his status for an upcoming Washington Wizards season.

Arenas had a "moderate amount of debris" removed from the knee after experiencing swelling and discomfort during his rehabilitation. The Wizards offered no timetable for his return — beyond the fact that he obviously won't be ready for the start of training camp next week — but Arenas told The Washington Post that he plans to be back on the court in early December, which would rule him out for the first month of the season.

The surgery is the third on the knee in 17 months for Arenas, who missed 69 regular-season games last season and had to shut himself down in the playoffs. It also raises more doubt about the wisdom of the Wizards' decision to give him a six-year, $111 million contract in July.

Arenas first hurt his knee in a game against Charlotte in April 2007. He tried to rush back and was playing in summer league games a few months later. The overzealous approach resulted in a second operation in November, causing him to miss most of the season.

Arenas vowed to take a more cautious approach to rehabilitation this summer, but the knee has not responded the way he would like.

The doctor who performed the operation Wednesday said debris buildup is common in Arenas' type of injury, and that an MRI showed the knee to be structurally sound.

"This was a proactive procedure that will enhance his rehabilitation process," said Dr. Marc Connell, the Wizards' team physician.

Despite the knee problems, the three-time All-Star decided to opt out of his contract at the end of last season and make himself a free agent. He re-signed with the Wizards, saying he accepted $16 million less than what was offered because he wanted to give the team more flexibility under the salary cap. Nevertheless, the $111 million deal was the richest in franchise history.

Arenas has proven to be one of the most exciting players in the NBA when healthy, averaging 22.8 points, 5.5 assists and 4.2 rebounds in his seven-season NBA career.

The Wizards' hopes of becoming a top Eastern Conference team have been disrupted by injuries to top players for the past two seasons. This was the season, they hoped, that everyone would stay more or less healthy.

"He had worked extremely hard over the summer and we know how much he's looking forward to returning to help the team," team president Ernie Grunfeld said. "However, our team has proven its resiliency in dealing with injuries in the past and we're approaching the start of training camp with confidence that they will once again compete at a high level until Gilbert's return."