© Stan Szeto-USA TODAY Sports

SANTA CLARA – With two weeks before the 49ers’ season opener in Tampa Bay, Florida, there’s a bit of sorting out to do on the offensive line. Following a season-ending injury to swing tackle Shon Coleman and a pair of preseason performances which featured an unhealthy dose of drive-killing offensive line penalties – starters included – head coach Kyle Shanahan and general manager John Lynch need players to step up.

Coleman provided reliable insurance for Joe Staley and Mike McGlinchey. Now rookie Justin Skule and veteran Sam Young are next up as the swing tackle backups (it’s unclear if the 49ers would take two tackles, but based on Lynch’s comments, the preference seems to be for the rookie Skule if it indeed comes down to him and Young).

“O-Line depth, when you have it, it’s rare,” Lynch said on KNBR on Thursday. “We felt like we bolstered it a little bit. Shon Coleman, he’s a guy we traded for going into last year, and he really developed, I think was probably as improved as any player on our roster through this offseason. That really hurt to see him go down because we really felt like we had another starting tackle as our swing guy, so now the pressure goes on a guy like Justin Skule from Vanderbilt, a rookie. But he’s got to step up his game. Sam Young, we went out and got.”

Coleman’s injury has been compounded with limited preseason game snaps for Staley and McGlinchey, center Weston Richburg remaining on the physically unable to perform list (although he’s in line to practice as early as next week) and both Mike Person and Joshua Garnett yet to play in a preseason game. It has paved the way for second-year guard Najee Toran and Skule (and even Young in his first preseason appearance) to take a dizzying number of snaps.

The frustrations of youth

Toran and Skule led all offensive players with 45 snaps in the preseason Week 2 game against the Denver Broncos. Young was fourth, behind Kendrick Bourne, at 37 snaps.

Skule was second (64 snaps) and Toran third (55 snaps) in snaps taken in the preseason Week 1 opener, with tackle Willie Beavers (67 snaps) falling out of favor after a howler of a game with three penalties (including a pair of back-to-back holds). Against the Cowboys, Toran had the fifth-highest Pro Football Focus ranking on the 49ers at 72.9, while Beavers was dead last at 40.9.

Both Skule and Toran represent the most likely (but far from secure) backups at guard and tackle, respectively. While they have had solid camps, those team-leading snap counts, especially against the Broncos, highlighted the drawbacks of their youth. In Week 2, Skule had a false start (also had a hold in Week 1) and Toran had a pair of holds, was beaten on a sack, and while shifted over center (a position he told KNBR he hadn’t played until he was slotted there for both preseason games), had a fumble on a bad snap to Nick Mullens under center.

To be clear, there were plenty of other linemen to commit penalties, especially in Week 1 (Beavers with his three holds, Daniel Brunskill and Christian DiLauro with one each, plus a few special teams and illegal shift penalties), but the other names to struggle are unlikely to make the roster, while Skule and Toran, at the very least, are strong contenders.

“It concerns me,” Shanahan said Tuesday. “You need to be able to block and you need to be able to do it without holding and we’ve gotten way too many of those in these last two weeks. It’s something that we definitely have to improve.”

Those mistakes found Shanahan calling on the line to sort it out in the final two games.

“Depth in an O-Line is something that every team is trying to work at and we need some guys to step up,” Shanahan said. “We’ve lost the two guys who were competing at guard, with Person and Garnett. That’s opened up some opportunities for these guys and that’s why they’ve been there a ton in these two games. They have had some really good plays that show that they can play in this league. But, just like you guys have noticed, they’ve had too many penalties and they’ve had some bad plays. The good thing about this stuff is that we do have two more games. It’s something that we haven’t seen yet to where we can figure it out. We need more game tape and hopefully one of these guys will step it up.”

Humility bodes well for upstarts

Toran and Skule made no attempt to eschew the blame for their errors.

“It’s all on me,” Toran told KNBR of the fumbled snap. “You’ve got to get the ball to the quarterback.”

Skule’s attitude was no different towards his penalties.

“Obviously, you can’t have that,” Skule said. “It’s more of just a next play mentality. You can’t let the play before you beat you on the next play or any plays in the future.”

There’s no way to measure exactly how much another player’s approach and wisdom have rubbed off on others, but it’s pretty clear that having Staley in the locker room does nothing but benefit young offensive linemen. Staley, who said on Thursday he’s his “harshest critic,” reveled in a story about the worst game of his career; one which forever changed the shape of his nose, and how all he could think about was getting back to practice.

“I remember in Week 1 in 2012 in Green Bay, Clay Matthews whooped my butt. He had three sacks, had about six other pressures, one of the worst games of my life,” Staley said. “Nose was broken, still looks terrible. I just remembered wanting to be on the practice field. That’s where you want to be. You want to be on the practice field and work on what was wrong… I followed up the next week with probably one of the best games of my life.”

Those crucial adjustments after learning harsh lessons define the NFL’s bets players.

From Toran, Skule and Young’s collective comments about coming into the NFL, the speed and strength required of linemen, and that of players on the other side fo the ball, seem to be the heaviest adjustments. Toran said he feels like he’s noticeably improved in that area since his rookie year last season. While much of that comes through experience, Young, a now 10-year-veteran, said he came into a very experienced offensive line room when he entered the league with the Cowboys, and it would do Skule and Toran well to be “sponges” in soaking up knowledge from players like Staley and McGlinchey.

By all accounts, that appears to be the case for both. Skule came into this team already with a pair of Vanderbilt alums – wide receiver Jordan Matthews and center/guard Wesley Johnson – who he’d known from when both returned to campus. Skule actually worked out with Johnson around the time of his Vanderbilt pro day, and found out Johnson signed with the 49ers shortly after he’d been drafted. Johnson’s message to Skule belied the brief bond they’d built:

“‘You just can’t get right rid of me.’”

Matthews told KNBR that he expects Skule to succeed in the NFL.

“I think Skule is a great player, he’s a great dude,” Matthews said. “He’s going to be a great O-Lineman, I think, in the league, strictly because of how humble he is. He’s a very low-key guy, he’s got that offensive line demeanor, but he’s tough. You probably wouldn’t know it sitting down eating with him, but he’s a very tough guy.”

That chance of success is undoubtedly improved with the twin-tackle combination of Staley and McGlinchey providing as ideal a pair of teachers as you could hope for a young offensive lineman.

“It’s been phenomenal,” Skule said. “They’ve really done a great job teaching me things, giving me little pointers, little cues to look at, but also just watching me throughout practice, like, ‘Hey, this is what you need to do, this is what you need to fix, this is how you can prevent that from happening.’”

But it’s not just Skule and Toran who’ve kept their ears open. Young, a Notre Dame alum, expressed his pleasure at having another Notre Dame tackle, McGlinchey, as well as Staley, to talk shop with.

“It’s been great,” Young said. “[McGlinchey] has been helping me pick up the offense and some of the techniques. He’s been a great guy, sharing some of our Notre Dame stories while we’re out there… Coming in the time I came in, you’ve got to be able to pick up the playbook and the techniques and what you’re asked to do. Some of the little nuanced details, being able to lean on more experienced guys has definitely been helpful for me.”

There’s one week to secure a spot

That humility and open-earedness is crucial for Toran and Skule, because neither is shoo-in for a roster spot. Young was praised as being “solid” by Shanahan in Week 2, and Garnett is back competing with Toran. On August 31, the roster gets cut from 90 players down to 53, and at least one of those players, possibly two – depending on how the numbers shake out – will be cut.

Don’t assume Garnett being back will do anything other than give him a chance. In March, the 49ers declined to pick up the fifth-year option on the former first-round pick who’s struggled to stay healthy his whole career. He’s only just started practicing after finger surgery with a cast on this week, and Shanahan said he hopes he’ll play Saturday, but is not certain. Lynch said Garnett needs to prove himself, in a fairly do-or-die tone.

“Josh is going to have to come show us that he’s ready to compete,” Lynch said on KNBR on Thursday.

Saturday’s third preseason game against the Chiefs will feature a first half with the starting offensive line, Richburg excluded (Ben Garland will continue to operate as the backup center and will likely make the roster). It is, however, unclear whether Mike Person will go a full half, considering the foot sprain he’s been working through. If he doesn’t, it will likely provide Toran his last preseason chance with the starters.

After that half, it’s going to be a genuine battle to secure the final roster spots, especially if the 49ers go light on offensive linemen to add depth elsewhere (10 defensive linemen is likely and three quarterbacks is in play, plus). The second half of Saturday’s game and the final preseason game, at home against the Los Angeles Chargers, will feature all backups. If the competition is still muddy right now, it’ll have to clarify itself by then.