SANTA CLARA -- The position group that figured to be the 49ers’ greatest strength is now the largest area of uncertainty as the team heads into the exhibition season.
The 49ers’ offensive line is generally regarded as one of the tops in the NFL. The only problem is that three starters from last season will not be on the field to protect quarterback Colin Kaepernick when the exhibition season opens Thursday at the Baltimore Ravens.
Here is how the 49ers stack up on the offensive line after two weeks of training camp:
Right guard: Alex Boone remains a holdout. He does not plan on reporting to camp without a new contract. The 49ers appear steadfast in their stance that they will not negotiate a new contract until he reports. Boone is paid like a backup. And he was a backup when he signed his deal in November 2011. He is no longer a backup. All indications are that he's not looking to break the bank, but the standstill remains.
An argument can be made that Boone has been the 49ers’ best guard since he took over as a starter in 2012. And, really, there’s no argument that Boone is the 49ers’ third-best offensive tackle. He could probably start at tackle for most teams in the league.
The good news: Joe Looney has looked solid in Boone’s place. The 49ers are keeping their fingers crossed that Looney can perform like he did when he got onto the field for extensive playing time against the St. Louis Rams last season.
Right tackle: Anthony Davis said he sustained a shoulder injury in Week 3 of last season. But it wasn’t until April 24 that he revealed that he had recently undergone surgery to repair the damage.
Obviously, Davis was not able to have a full offseason of strength training. And he still has not been cleared to practice. He will not be on the field Thursday against the Ravens. There’s been no timetable for his return to action. If he’s ready for the regular season, there have to be questions whether he’ll be in tip-top condition to perform.
[REWIND: Davis undergoes shoulder surgery]
Jonathan Martin has taken over at right tackle with the starting unit. The first couple weeks of camp have been rough at times. Martin had his hands full against the 49ers’ defensive line. Lawrence Okoye and Tony Jerod-Eddie have planted Martin on his backside during pass-rush drills.
Center: The 49ers had no interest in re-signing veteran Jonathan Goodwin. Daniel Kilgore has been used as an additional blocker in short-yardage situations for a couple of seasons. He appears to have a sizable lead in the competition over rookie Marcus Martin, who missed time at the beginning of camp due to an ankle sprain.
Kilgore is definitely ready from a physical standpoint. However, so much of a center’s job is mental. That’s where Goodwin could be missed. After all, Goodwin had 12 years of NFL experience of identifying defensive fronts and making critical adjustments.
[REWIND: Training camp preview: Offensive line]
Left guard: Mike Iupati is back to full strength from the fractured left lower fibula sustained in the NFC Championship game at Seattle. It was a clean break, which meant a straight-forward recovery and rehab.
Iupati is entering the final year of his original five-year contract. He is in line for a massive contract on the open market next spring. There is no indication the 49ers are close to a contract extension with the two-time Pro Bowl performer.
Left tackle: The 49ers’ best offensive player in training camp has been Joe Staley -- no question about it.
And Staley is certainly one of the most-valuable players on the team, too. Without Boone in camp, the 49ers do not have a proven, serviceable backup at the most important spot on the offensive line.