Boldin, who will turn 36 in October, was the leading receiver for the 49ers last season with 69 catches for 789 yards and four touchdowns. He’s played for Lions head coach Jim Caldwell in the past, when Caldwell was an offensive coordinator with the Ravens late in the 2012 season.
"Caldwell’s probably one of the better coaches that I’ve played for," Boldin said back in February, via the Detroit Free Press. "I love the way he goes about his business. He’s just a great guy and … probably every player in this league would like to play for Caldwell."
The Lions were forced to overhaul their receiving corps after Calvin Johnson announced his retirement back in March. Golden Tate remains in the fold, and the team signed Marvin Jones, Jeremy Kerley, Andre Caldwell and Andre Roberts.