Lane Johnson is used to position changes: In his college career he moved from quarterback to tight end to defensive end to offensive tackle. The Eagles spent the No. 4 overall pick on Johnson in April so he could play right tackle.

But just in case, the Eagles have been playing Johnson on the left side in practice.

The Eagles are preparing in case Jason Peters misses any time during the 2013 season. Peters, a four-time Pro Bowl player, missed all of 2012 with a ruptured Achilles tendon and has already missed three full practices this summer with a hamstring injury, including Monday's practice.

When Peters misses time during camp, Johnson replaces him. On Monday, Johnson was back at right tackle. The Eagles want him to be able to play both.

"I think it's a good sign," Johnson said. "There's not very many people who can play both. The more practice I get playing left and right is going to help me if something happens to Jason."

Coach Chip Kelly said Sunday that the Eagles would go with their best tackle combination if Peters is absent, even if that conflicts with continuity on the line. That combination is Johnson at left tackle and Todd Herremans, the starting right guard, bouncing outside to right tackle. Danny Watkins then fills in for Herremans at right guard.

"So, instead of saying in the Redskins game, 'Hey, we've got to move Lane, but he's never taken any snaps over there,' we had planned all along at getting Lane work at right tackle and left tackle," Kelly said.

Even if Johnson plays left tackle when Peters is absent, Herremans would not necessarily need to move to the right side to replace him. There's also the option of Dennis Kelly, who is out with a back injury.

"We're just making sure as you look down the road, we have some contingency plans on how it works," Chip Kelly said. Johnson "brings us the ability for a guy that can play both tackles, and to be honest with you, that's rare. There are some guys that are legitimate right tackles, and finding tackles in this league is very difficult."

Johnson said he needs more work on the right side than the left, because he's less comfortable there. That's why Johnson was back on the right side on Monday, with Allen Barbre playing left tackle. Johnson expects to continue on the right side for the next two days when the New England Patriots practice with the Eagles at the NovaCare Complex.

As much as the Eagles tout Johnson's versatility, what impresses them the most is his ability. With Johnson and Peters as bookend tackles, the Eagles offensive line could be significantly better than last season - and one of the best in the NFL. A former Oklahoma star, Johnson is still adjusting to the NFL, and his technique will continue to improve while working with offensive line coach Jeff Stoutland. But physically, he has the size and athleticism to be a longtime starter for the team.

"One thing I learned about the NFL is in college, you can take some plays off sometimes," Johnson said. "Here, every player is full-go, and nobody is giving up. Probably from a mental standpoint, that's the biggest difference."

Johnson's performance during the preseason will be one of the key areas to watch. Where he plays is also important. The Eagles need him prepared to play right tackle, but the team must also be careful not to rush Peters back from injury. And if Peters gets hurt during the season, the team is ready to move Johnson into his spot.

"I think when you get an opportunity in practice to go through some things and see them on film, there are some subtle differences, different foot up, some of those things," Chip Kelly said. "So it's just kind of giving us down the road, we've got a little bit of depth from that standpoint."

Contact Zach Berman at zberman@phillynews.com. Follow on Twitter @ZBerm.