updated 6:29 p.m. ET Oct. 8, 2008

BOSTON - New England Patriots quarterback Tom Brady underwent surgery on his left knee this week, a month after he was sidelined with the season-ending injury, The Boston Globe said.

The paper reported Wednesday that the operation was performed Monday in Los Angeles. Brady’s replacement, Matt Cassel, said he tried calling him.

“I haven’t gotten a return phone call yet,” he said. “I’m sure he’s just resting.”

Patriots spokesman Stacey James declined comment. Coach Bill Belichick refused comment during his regular news conference Wednesday at San Jose State, where the team is practicing for Sunday’s game at the San Diego Chargers.

“We’re not going to comment on anybody’s situation,” he said. “We’re not going to get into a daily update.”

Belichick sidestepped two other questions about Brady.

Asked if he had talked to the quarterback, the coach said, “I’m just worried about the San Diego Chargers right now. That’s what we’re focused on.”

Will the NFL’s reigning MVP and two-time Super Bowl MVP keep working with the Patriots’ other quarterbacks as he had done since the injury?

“His first responsibility is to do what he needs to do and then we’ll go from there,” Belichick said.

A spokesperson for Dr. Neal S. ElAttrache, a Los Angeles orthopedist who the Globe said Brady had chosen to do the operation, said she could not comment because Brady had not given permission to discuss his case.

Patriots chairman and owner Robert Kraft, team president Jonathan Kraft, several players and Brady’s agent, Donald Yee, did not return phone calls seeking comment.

Brady was hurt in the first quarter of the season opener on Sept. 7 when he was hit by Kansas City safety Bernard Pollard. Cassel replaced him and the Patriots won 17-10. Brady reportedly tore ligaments in his knee, but the team has not announced the extent of the injury.

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