Breaking Down San Francisco 49ers' 2015 Offensive Line After Anthony Davis Exit

Just when the San Francisco 49ers thought they had a settled roster, they were hit by another surprise departure. Offensive tackle Anthony Davis recently announced he is going to take some time away from the game, reported by the team's official site, becoming the fourth big-name 49er to retire this offseason and leaving their offensive line looking shaky and inexperienced.

Davis had held down the right-tackle spot on the O-line since being drafted by the Niners in 2010. But with the former Rutgers man and guard Mike Iupati—who left for the Arizona Cardinals in free agency—out for the picture, how will San Francisco fill the void in the trenches in 2015?

The Niners prepared for the loss of key players on the O-line by drafting plenty of interior linemen in recent years. However, Davis' loss has left them a little light at tackle, meaning that something of a reshuffle could be required to get the most out of the players San Francisco has up front.

Head coach Jim Tomsula revealed that Erik Pears—signed as a free agent following five seasons with the Buffalo Bills—has been practising at right tackle during minicamp. Alex Boone, who skipped voluntary team activities earlier in the offseason, getting work at the left-guard spot vacated by Iupati.

However, going forward, it may make more sense for Boone to kick outside despite Pears' considerable experience at tackle. Pears endured a dreadful year after moving to right guard in 2014 but did a solid job during the time he spent playing at right tackle with the Bills, except in one area: run blocking.

In that respect, given that the 49ers have plenty of depth on the inside, moving Boone to right tackle makes sense. The former Ohio State Buckeye has the versatility to play on the outside and has received a positive grade in run blocking from Pro Football Focus in every year of his career with the Niners.

Yet if the 49ers want to have the flexibility to kick Boone to right tackle, then they will need to have plenty of confidence in what would effectively be an all-new interior line.

Marcio Jose Sanchez/Associated Press

As it stands, Daniel Kilgore and Marcus Martin would be competing for the center job, with the loser likely to take the other guard spot, while Brandon Thomas would appear to be the best candidate to take Boone's left-guard role were he to switch to tackle.

Kilgore was very impressive in the first seven weeks of the 2014 season before suffering a season-ending leg injury. He received an overall grade of 4.1 from PFF for his play last year, making him the favorite to win the competition ahead of Martin, who struggled mightily by comparison in his rookie year after being picked in the third round.

But things already appear to be looking up for Martin, with Matt Barrows of the Sacramento Bee indicating that the former USC player has improved his physical shape from last year.

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Martin, who had what can politely be called a Rubenesque build when he started eight games at center as a rookie last season, has a leaner look this year in both body and face. Last year, he said, he played in the 330-pound range. He is currently in the 320s with the intention of getting into the three-teens by the start of the season.

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With Tomsula apparently stressing a desire for the Niners to run a faster-paced offense in 2015, Martin's transformation is a necessary one and should allow him to excel in the 49ers' running game, which has long been dependent on athletic linemen with the ability to pull effectively.

But there is plenty to be said for the athleticism of Thomas, another third-rounder in 2014 who perhaps would have been a first-round pick if not for the torn ACL he suffered in the pre-draft process. Thomas twice earned All-ACC honors with Clemson and was praised for his ability on the move in Nolan Nawrocki's scouting report for NFL.com

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Good size with very long arms and big hands. Quick out of his stance. Knee bender with good balance and body control. Solid base. Places his hands inside and can pop and recoil. Strong-handed puncher with good grip strength once he latches on. Athletic, efficient mover. Light on his feet to step to the second level or pull. Can maneuver and throw his hips in the hole. Climbs to the second level. Three-year starter who played tackle. Held his own against Jadeveon Clowney without help.

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Thomas' work-ethic in OTAs delighted Tomsula, but the wild card who could perhaps keep him out of a starting job by allowing Boone to stay inside is rookie Trenton Brown.

Brown was selected in the seventh round amid concerns over his weight but has received reps at right tackle in Davis' absence and has been quick to make a positive impact. A mammoth athlete at 6'8" with 36-inch arms, Brown has dropped his weight down from 387 pounds to 350, according to Barrows, who reported that the former Florida Gator was beaten just once in pass-rush drills during OTAs, with Aldon Smith the only man to get the better of him.

John Raoux/Associated Press

For a 49ers O-line that gave up 52 sacks last season, Brown's apparent quick progress should come as a pleasing development but must be taken with a pinch of salt, given that he has yet to practice wearing pads. He could, though, present San Francisco with a dilemma should he continue to look good in training camp and preseason.

What will obviously count against Brown is his lack of experience. Pass-protection skills are a must, but the key for San Francisco's O-line will be striking a balance between experienced players and those athletic enough to play in an up-tempo offense.

The likes of Joe Staley and Boone have the benefit of experience and should have no difficulty dealing with a fast-paced style of play. Boone's proficiency as a run-blocker should see him favoured for the right-tackle spot over Pears, which would place a lot of pressure on what would be a young interior line.

San Francisco received plaudits for the selections of Martin and Thomas in 2014. The Niners still have plenty of depth on the O-line, but with Davis now gone, it is time to see if the adulation they earned for those picks was justified.

Nicholas McGee is a San Francisco 49ers featured columnist based in Leeds, England. Follow him on Twitter @nicholasmcgee24.