The 49ers signed fullback Chris Hetherington releasing guard Tony Wragge to make room for the 10-year veteran. Hetherington was cut by the Raiders on Saturday after two seasons with the club. The Yale graduate also has played for Indianapolis, Carolina and St. Louis. The 49ers need depth at the position because backup fullback Steve Bush might be forced to play tight end if injured starter Eric Johnson and new acquisition Trent Smith aren't ready to go in the season opener against the Rams on Sunday. Rookie Billy Bajema is the 49ers' only healthy tight end who went through training camp with the club. Wragge was out of football last season after trying to make the Cardinals' roster in the previous two seasons. He played for the Los Angeles Avengers in the Arena Football League last spring.