Veteran left-hander Kent Mercker will undergo season-ending reconstructive surgery on his left elbow, the Reds said Monday. The 38-year-old Mercker was placed on the disabled list Saturday after pitching a scoreless inning in relief Friday night in Philadelphia. He was examined Monday by Timothy Kremchek, the Reds' medical director, who scheduled surgery for Thursday. Mercker has been on the disabled list three times this season because of elbow problems.