SANTA CLARA -- Alex Boone, the 49ers' starting right guard since 2012, may skip voluntary offseason workouts in search of a new contract, ESPN first reported.
Boone has two years remaining on a contract he signed in December 2011, when he was primarily an extra blocker on short-yardage plays and on special teams.
The 49ers, who began offseason training activities Monday, have several starters entering the final seasons of their respective contracts: quarterback Colin Kaepernick, wide receiver Michael Crabtree, left guard Mike Iupati, running back Frank Gore and cornerback Chris Culliver.
Boone has been with the 49ers since going undrafted out of Ohio State in 2009. He's scheduled to make $2 million in base salary this season, $1.2 million in 2015.
The 49ers offensive line returns mostly intact aside from center Jonathan Goodwin's exit as a free agent. Daniel Kilgore, Adam Snyder and Joe Looney are top reserves and all are capable of playing guard.
Earlier this month, the 49ers used third-round draft picks on USC center Marcus Martin, who said he's also learning both guard positions, and Clemson's Brandon Thomas, who'll likely miss his rookie season recovering from April knee surgery.
Of the 49ers' 12 draft picks, Martin is the only one unsigned. Wide receiver Bruce Ellington, a fourth-round selection, signed his four-year contract Tuesday.