PORT ST. LUCIE — The Mets are getting the day off tomorrow, although not all of them. Mike Pelfrey, sidelined since last week by a strained muscle in his lower left leg, is scheduled to pitch a bullpen session in the morning. The session is a prelude to Pelfrey returning to the rotation for a start Saturday at home against the Nationals. Fifth-starter candidate Jonathon Niese, meanwhile will pitch to Met minor leaguers immediately after Pelfrey throws so Niese can get his turn in.