EAGAN, Minn. -- One week into training camp, the Minnesota Vikings' offensive line is already looking to its reserves to fill the void for injured players.

Right tackle Rashod Hill has missed several practices with an illness, which thrust rookie Brian O'Neill in with the first team. On Tuesday, veteran guard Mike Remmers injured his left ankle during a goal-line rep and left practice early in a walking boot.

Underneath all the layers of optimism surrounding this season lies the team's biggest concern: the strength of the offensive line -- namely solidifying the right side -- and its level of depth.

This group was struck with unbelievable tragedy days before the start of camp when veteran offensive line coach Tony Sparano died unexpectedly at age 56. In an effort to provide stability, coach Mike Zimmer made in-house promotions, naming Clancy Barone and Andrew Janocko co-offensive line coaches. The blocking schemes, terminology and players' footwork won't change, and many of Sparano's philosophies will carry over.

"Tony and I always talked about O-line play," Barone said. "From the day that I got hired, we were always watching tape together and he was asking me that, with my background, 'How did you handle this situation or this look?' He and I were on the same page quite a bit no matter what, which makes it a lot more helpful."

But the injuries have added further disruption. Multiple league sources confirmed to ESPN that Remmers is expected to miss a week or more while recovering from his injury. One source notes that the injury is "not anything serious" that could jeopardize Remmers starting in Week 1 and that the Vikings may choose to rest the right guard during the preseason and not rush him back. Hill's illness isn't expected to keep him out long.

In the meantime, Minnesota has shuffled its offensive line combinations around in a handful of ways. O'Neill is at right tackle in place of Hill. Nick Easton has taken over at center while Pat Elflein continues to recover from offseason ankle and shoulder surgery. Tom Compton and Danny Isidora have taken snaps at left guard with the first team, while Isidora moved over to right guard after Remmers went down.

The early absences from starters could help develop depth along the offensive line and also may help the Vikings figure out who they want to keep as they whittle down the roster four weeks from now. But at this point, should Minnesota feel the need to stabilize this unit further, it might have to come via a trade or after a lineman is cut from another team during camp. The free-agent market has been picked over, leaving veteran guard/tackle Luke Joeckel as one of the few options available.

The shuffling is something Minnesota had to do far too many times over the past two seasons. In 2016, injuries decimated the unit, forcing the Vikings to use eight different starting combinations. It wasn't that much different last season, when Sparano mixed up his starting personnel seven times after injuries began in Week 5 and were a constant presence throughout the year.

The good news for Elflein is that the second-year standout can be activated off the physically unable to perform list at any time during the preseason. The center has spent part of camp lifting weights and taking isolated snaps during practice with head strength and conditioning coach Mark Uyeyama. Zimmer said he knows the timeline for Elflein's return but would not comment on its details. Sources indicate it isn't too far off, though. But like Remmers, the level of concern in rushing Elflein back into action takes precedence and could keep him out as a precautionary measure.

In the meantime, Elflein has taken a different approach to building the much-needed chemistry with quarterback Kirk Cousins.

"I've been out here standing next to him at practice and just going over the calls, the sequence of how a play operates with protections, different looks," Elflein said. "We've been talking about it. I feel like that's the best way to build that right now if you can't actually get out there and get game reps or practice reps. Just doing what we can to build that chemistry and what his thought process is and what mine is and converging those together to make it a well-oiled machine."