Ryan Mundy stepping in for an injured Antrel Rolle

Antrel Rolle is expected to be sidelined with an ankle sprain at least until the regular season opener against the Dallas Cowboys, and in his place steps in one of the New York Giants' most notable free-agent signings.

Ryan Mundy, formerly of the Pittsburgh Steelers, will start alongside Stevie Brown in the Giants secondary until Rolle is healthy.

[Related: Rolle sheds walking boot]

It's not a position Mundy is unfamiliar with; he's had to fill in for an injured Troy Polamula quite often is recent years. And yet again, Mundy is tasked with filling in for the centerpiece of a defense.

"This is a road that I'm very familiar with from my time at Pittsburgh, my five years there," Mundy said. "I was a primary backup to Troy and Ryan (Clark), so this a role that I know how to function is and I know how to prepare for."

There is, of course, a learning curve, as Mundy switches from Dick Lebeau's scheme to that of Perry Fewell.

Like the Steelers, the Giants utilize a three-safety approach at times, but there are some nuances Mundy still has to get used to. And with each passing day, Mundy said, he's getting more accustomed to them.

"It's a work in progress," he said. "I'm in here working hard, trying to better my understanding of the defense, and it's an exciting process. You know everyone has been very helpful from the coaches to the teammates, and I think I have a pretty good grasp, but it's not where I want to be yet."

For Fewell, having Mundy has a backup is a luxury. Last year, when Kenny Phillip went down due to injury, it was Brown who was thrust into the starting unit -- a Brown nobody could have predicted would wind up leading the team in interceptions.

But with Mundynext on the depth chart behind Rolle and Brown, there's a higher degree of comfort. Despite the fact he's still learning the schemes, Mundy has shown he's a knowledgeable football player and a savvy vet, and now will have to prove he's an asset in New York.

"(Mundy is) a sound football player, a smart football player. I'm happy that he's with us. He's very conscientious and physical," Fewell said. "He's very knowledgeable as far as the defense is concerned. He does not have the experience and the background that Antrel has because he hasn't been in the system as long, but he's very conscientious and working with Stevie Brown. He'll be fine."

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