LOS ANGELES -- David Beckham could miss the rest of the Los Angeles Galaxy's season after being diagnosed with a sprained right knee Thursday. The English midfielder underwent an MRI exam that confirmed he sprained the medial collateral ligament in his knee, the team said in a statement. Beckham, 32, was injured in a tackle with Pachuca midfielder Fernando Salazar in the first half of Wednesday night's SuperLiga title match. The Galaxy lost 4-3 on penalty kicks. He was expected to be out about six weeks, and will immediately begin rehabilitation, the team said, although Beckham himself told radio show host Ryan Seacrest Friday that a doctor had estimated his injury would take 8-10 weeks to heal. That would place his return in a best-case scenario at mid-October, when the Galaxy would have three regular-season games remaining -- against Toronto FC on Oct. 13, New York on Oct. 18 and at Chicago on Oct. 21. "It's just gone from one thing to another thing,'' Beckham said Wednesday night. "Maybe it's time for me to just say, 'I need the rest,' and get it right and don't come back until it's right.'' He had already been nursing a left ankle injury that caused him to miss seven games since joining the team July 13. That injury occurred while playing for England on June 6. Beckham's extended absence deals a serious blow to the already slim chance the Galaxy had of making the playoffs. Its Major League Soccer record is 3-10-5 -- last in the Western Conference. "The biggest thing is that we're markedly better when he's on the field,'' Chris Klein said after Wednesday's loss. "Just having his presence around the guys gives us a much needed boost. When he's not there, it hurts us.'' The Galaxy declined to make any team officials available for comment Thursday. Coach Frank Yallop was clearly frustrated about the string of injuries that has devastated his team this season, especially the ones involving Beckham. "He shouldn't play, to be honest. He's hurt, but he's playing,'' Yallop said Wednesday night. "That shows the character of him and it shows the character of the team because he lifts the team when he plays. "It's hard because he's struggling with injury. He's trying his best.'' Beckham's latest injury also means he won't be joining England's national team. He had planned to fly to London on Sunday for 10 days with the team as it prepares to play Israel and Russia in two Euro 2008 qualifying games.