The crowd of 37,796 at Fenway Park stood and cheered when John Lackey walked off the mound in the sixth inning yesterday afternoon, having pitched effectively against the Athletics in his return from the disabled list. Lackey kept his head down as he approached the dugout, not acknowledging the tribute with a wave or tip of his cap. After the Red Sox finished off a three-game sweep with a 6-3 victory, Lackey was told that he hadn't heard cheers like that very often at Fenway.