The “Mythical Creature” returns.

Andre Dillard once gave Jason Peters that moniker, and the 38-year-old offensive lineman’s sustained unwillingness to begin the five-year countdown before his induction into the Hall of Fame certainly has added to his legend.

But Peters’ coming back for a 12th season with the Eagles – and 17th overall – comes with a caveat: It won’t be as the starting left tackle. He will assume the right guard position vacated by Brandon Brooks’ Achilles’ tendon rupture as Dillard begins his tenure as Peters’ successor.

The Eagles, on paper, improved Tuesday with Peters a likely upgrade over the inexperienced Matt Pryor. They also retained a valuable off-field commodity who has tutored many younger offensive linemen and will continue to assist in Dillard’s development.

For those reasons alone, it was probably worth the one-year, $3 million guaranteed contract.

Of equal importance was Peters’ value as a swing tackle in case of injury, and specifically on the left flank should Dillard struggle. The Eagles improved their roster, clearly, but they also created a situation in which their unproven 2019 first-round draft pick will have to perform with the Yeti of tackles peering over his shoulder.

Dillard might be motivated by such a dynamic, but there have been internal concerns about the Washington State product’s mental makeup, and having Peters around might not be a conducive environment for an unsure second-year tackle.

The Eagles owe it to their 2020 chances to cover their bases, and Brooks’ season-ending injury last month placed them in a vise. They also had virtually no offseason except, of course, a virtual one, and the uncertainty surrounding training camp and the preseason could further hinder Dillard’s progress.

» READ MORE: The Eagles listen when Jason Peters talks

But the significant investment and fallout should he have a setback suggests that it might have been in the Eagles’ best interest to look elsewhere for a solution. Peters wouldn’t have signed had he not been willing to take a lesser role, but he was still competing at a high level by season’s end and is as prideful as athletes come.

“I still can get it done,” Peters said just after the Eagles’ playoff loss to the Seahawks in January. “If I couldn’t get it done, I’d just walk away. But I can still go.”

The rest of the NFL thought otherwise, as least based on his positional and contract demands once the Eagles decided to allow Peters to enter free agency. He had options in March, according to his agent, Vince Taylor, but opted to wait for the “right opportunity,” which presumably came Tuesday.

“His plan has always been to move to guard,” Taylor said.

» READ MORE: His Eagles teammates say this about Jason Peters: Don’t ever count him out | Jeff McLane

Peters mentioned an eventual move inside as far back as 2015, but he would often bristle anytime the topic was broached, and when he was asked before the final regular-season game of last season about nearing the end of his career, he challenged a reporter.

“You tell me somebody’s that’s better than me and I’ll walk away from the game,” he said. “You got somebody?”

Inside the Eagles locker room, there wasn’t a better alternative at left tackle, and that will likely be the case if and when this coming season begins. Players are the least affected by outside considerations and there will have to be a period of ignoring the figurative elephant in the offensive line meeting room.

But Peters comes with durability concerns. He has missed a third of regular-season snaps over the last three years due to various injuries. The 6-foot-4, 300-something-pound freak of nature has defied age, two Achilles’ ruptures, a torn ACL, and countless other bumps and bruises to play at this stage, but for how much longer?

And for how well at a position he has never played? Guard is generally considered an easier task because there is help on either side. Tackles are often on islands, particularly in pass protection. But there are subtle nuances to interior blocking – more shifting responsibilities, for example – and Peters will also be moving to the right side.

He gets to play alongside two of the best at their positions – center Jason Kelce and right tackle Lane Johnson – but that, too, will require an adjustment.

The Eagles could have gone with Pryor, their 2018 sixth-round pick who fared well in the playoff loss to the Seahawks after Brooks’ season-ending shoulder injury. Peters, though, also accounts for the loss of swing tackle Halapoulivaati Vaitai and the unknown of having project Jordan Mailata step into that role.

When the Eagles announced in March that they had agreed to a mutual parting, they didn’t close the door on a Peters return. But it was seen as a symbolic transition to a younger roster and a move from the previous two offseasons when general manager Howie Roseman kept retaining veteran pieces who were part of the 2017 Super Bowl season.

If anyone was worth another go-around, it was Peters. Brooks’ injury created a vacuum that allowed for the Eagles to downplay the negative implications it might have on Dillard’s psyche, while also hyping the positives it could bring in the new left tackle’s growth.

But Peters can mentor Dillard only so much, and only if he’s open to counseling from his potential replacement. At what point could his return come at the expense of the future? The Eagles likely calculate that risk. A Mythical Creature could test its bounds.