Mark Sanchez was a lefty passer Sunday. (Julio Cortez / AP)

Mark Sanchez was on the field, throwing passes with his left arm Sunday before the New York Jets’ game against the Tampa Bay Buccaneers and now we know why.

Sanchez suffered a separated shoulder, Fox Sports’ Jay Glazer reports, when he was put back into a preseason game in the fourth quarter by his coach. Sanchez also has a partially torn labrum, Glazer and ESPN’s Chris Mortensen report, and he will be examined by Dr. James Andrews this week.

Sanchez, of course, is inactive today and, with Brady Quinn being cut Saturday, the Jets will have Matt Simms backing up rookie Geno Smith.

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