Quaterback Trent Dilfer, who spent this past season as a backup with the San Francisco 49ers, said yesterday that he is retiring from the NFL. Speaking during a teleconference in advance of this weekend’s American Century Celebrity Golf Championship in South Lake Tahoe, Dilfer said he would make a formal announcement in the coming days about ending his 13-year NFL career. The 36-year old Dilfer threw for 1,166 yards with seven touchdowns and 12 interceptions in seven games, including six starts last season with the 49ers. Over his career, Dilfer passed for 20,518 yards, 113 touchdowns and 129 interceptions. He helped lead the Baltimore Ravens to a victory in Super Bowl 35 after the 2000 season.