Flushing, NY -- (Sports Network) - New York Mets closer Billy Wagner will need season-ending surgery on his left elbow and will be out of action for a full calendar year.

Wearing a protective sleeve on his left elbow, Wagner tested his arm Sunday between games of a day-night doubleheader against Philadelphia and threw pitches to teammate Gustavo Molina. He cut the session short and walked off the field after experiencing discomfort in the elbow.

An MRI exam taken Monday revealed that Wagner has suffered a torn MCL in the elbow.

The hard-throwing Wagner was in the middle of his eighth consecutive season with 20 or more saves, having notched 27 this season when he went on the disabled list in early August. He has posted a 2.30 earned run average and 52 strikeouts in 47 innings pitched.

The Mets saw their lead in the NL East fall to 1 1/2 games over Philadelphia, after the Phillies beat Florida, 8-6, Monday night.