San Francisco ? When the game of Koy Detmer’s life abruptly ended because of a scary elbow injury, A.J. Feeley capably backed up the backup – and the Philadelphia Eagles rolled on to an impressive win.

Filling in tremendously for Donovan McNabb, Detmer passed for 227 yards, threw two touchdowns and rushed for another score before leaving because of a dislocated left elbow late in the Eagles’ 38-17 victory against San Francisco on Monday night.

McNabb is expected to miss the rest of the regular season because of a broken ankle, but in Detmer’s first start since 1999, he was outstanding for nearly three quarters. Using all of his receivers in coach Andy Reid’s unpredictable game plan, Detmer carved up the 49ers’ confused secondary and staked the Eagles (8-3) to a big lead in a one-sided meeting of division leaders.

Detmer, a career backup who had thrown just 17 passes since 1999, completed 18 of his 26 throws until he landed heavily on his left arm as Chike Okeafor knocked him to the ground after completing a 24-yard pass to Jeff Thomason.

Feeley, the third-stringer who hadn’t thrown a pass all season, hit Chad Lewis for a 1-yard TD moments later – and the Eagles were all but assured of a conference victory that might turn out to be very important when playoff seedings are determined in five weeks.

Brian Mitchell returned a punt 76 yards for a touchdown, while Todd Pinkston and Antonio Freeman caught TD passes from Detmer as the Eagles mowed down the 49ers’ defense even without McNabb or a consistent running game.

Philadelphia wide receiver Todd Pinkston (87) hauls in a reception above San Francisco cornerback Mike Rumph (24) during Monday's game in San Francisco.

Terrell Owens had 13 catches for 166 yards and two TDs, but in spite of a warm night on Candlestick Point and the Eagles’ desperate quarterback situation, the 49ers were terrible on both sides of the ball.

The Niners (7-4) still lead the NFC West by two games, but they’ve lost consecutive games for the first time since midway through the 2000 season.