Boston Red Sox third baseman Bill Mueller has undergone arthroscopic surgery to relieve swelling in his right knee, but might be able to return in time for opening day.

Dr. David Zeman performed the surgery on Monday. Mueller can resume full baseball activities in four weeks, team spokesman Glenn Geffner said.

Zeman also operated on Mueller’s right knee last May and the player missed 37 games, though he complained of soreness through the end of the season. Zeman also operated on Mueller’s left knee in 2002.

The 2003 AL batting champion, Mueller batted .283 with 12 homers and 57 RBIs in 110 games last season. He batted .321 in the playoffs, including a .429 average in the World Series as the Red Sox won it all for the first time since 1918.

His biggest hit came in the fourth game of the AL championship series against the Yankees. With the Red Sox trailing 4-3 in the ninth and New York closer Mariano Rivera on the mound, Kevin Millar drew a no-out walk. Dave Roberts pinch ran for Millar and stole second base before Mueller singled to drive in Roberts.

Boston won four straight to beat New York and then swept the St. Louis Cardinals in the Series.

AP-ES-02-10-05 1727EST