The 49ers signed wide receiver Brett Swain, who the club determined had the most impressive tryout Tuesday at the team's practice facility in Santa Clara, a source said.Swain, 26, played 16 games for the Green Bay Packers last year, and appeared in the Super Bowl. He joins center Jonathan Goodwin as the only 49ers with Super Bowl rings.Swain (6-foot, 200 pounds) appeared in 16 games last season for the Packers, mostly as a special-teams player. He caught six passes for 72 yards. Swain entered the league as a seventh-round draft pick from San Diego State.The 49ers have yet to announce the signing, as they determine how to clear room on their 53-man roster for Swain.The 49ers were in the market for a wide receiver after Joshua Morgan sustained a potential season-ending leg injury Sunday in the team's 48-3 victory over the Tampa Bay Buccaneers. Morgan underwent surgery on his broken right lower leg on Monday.Swain had the best overall performance during a workout Tuesday that included veteran wide receivers T.J. Houshmandzadeh, Chris Chambers, and Brian Finneran, as well as practice-squad players Joe Hastings and John Matthews.