Peters, a four-time Pro Bowl player, suffered the injury near the end of Friday's practice in a team drill. He limped out of the indoor practice facility accompanied by one of the team's trainers.
"Jason Peters came out with an ankle, Achilles tenderness," Eagles coach Andy Reid said. "Nothing looks to be too serious, so they're going to check it out and see how he's doing. He seems to be doing well now."
However, when the team's injury report was announced a few minutes after Reid's brief press conference ended, Peters was listed as questionable, not probable. Questionable gives a player a 50-percent chance to play. Probable would have meant there was a 75-percent chance.
King Dunlap, a seventh-round pick out of Auburn in 2008, replaced Peters at left tackle for the final few sets of practice. Dunlap would make his sixth career start in four years if Peters cannot play. Ironically, Dunlap made his first career start a year ago vs. Atlanta in place of Peters, who was out with a knee injury. The Eagles won that game, 31-17.
"I always prepare myself as if I'm going to play, and then if I do have to get in there, it's no big deal," Dunlap said. "I definitely prepare better now than early in my career. I got caught off guard a couple of times where I didn't take it serious enough, and honestly I wasn't as ready as I should have been.
"(A) game in Oakland (in 2009), I didn't prepare the way I should have and I wasn't ready. I learned my lesson. Ever since then, I prepare as if I'm the starter, whether I'm starting or not. It's one thing to say, 'I know I'm only one play away.' But it's another thing to really prepare like it's true."
Peters, who the Eagles acquired in a trade with Buffalo for three draft picks before the 2009 draft, has been Philadelphia's best lineman the past two years. When Reid and new line coach Howard Mudd reshuffled the unit this brief offseason, Peters was the only one to stay put.
There is a new left guard next to him in Evan Mathis, who was signed as a free agent from Cincinnati, a new center in rookie sixth-round pick Jason Kelce, a new right guard in Kyle DeVan, acquired off waivers from Indianapolis, and a new right tackle in Todd Herremans, a converted guard.
Since coming to the Eagles in 2009, Peters has missed just three games.
NOTES: Backup defensive end Darryl Tapp is out Sunday with a pectoral injury. Former CFL star Phillip Hunt is expected to see his first NFL action in his place. ... Backup linebacker Akeem Jordan is doubtful with a shoulder injury. ... Peters, cornerback Dominique Rodgers-Cromartie and backup quarterback Vince Young are questionable. Rodgers-Cromartie practiced yesterday and is expected to play. Reid said he was leaning toward keeping Young out another week.