Buffalo Bills coach Chan Gailey was stumped last week when he was asked where his team’s secondary would be without rookie cornerback Stephon Gilmore.

“I have no clue,” Gailey said. “I don’t know how to answer that question, to be honest with you.”

One suggested answer: In a world of hurt.

Gilmore has been a starter seemingly from the moment the Bills made him the 10th overall pick in April’s draft out of South Carolina. He’s played basically every meaningful snap of the season, 97 percent overall, and in recent weeks has been tasked with guarding the opposition’s No. 1 receiver.

That’s a change from the start of the season, when the Bills asked their corners to play “halves,” guarding one half of the field regardless of who’s lined up there.

“He’s playing very well. He’s doing a good job. He’s become a better player, to me, each week,” Gailey said. “He’s becoming more knowledgeable. He’s understanding the game and what he’s got to get done.”

Gilmore lobbied the Bills’ defensive staff for the chance to guard the other team’s best receiver.

“That’s what type of player I want to be. I want to guard their best receiver and make him work for everything he can get,” Gilmore said.

That job started in Houston against the Texans’ Andre Johnson, after left cornerback Aaron Williams was hurt. Gilmore lined up on Brandon Lloyd in New England in Week 10, then checked Miami’s Brian Hartline on Thursday night.

“I think I had to get a little bit more comfortable out there on the field. Now that I feel comfortable, I feel like pretty much if I study the receiver, I can guard whoever they want me to,” Gilmore said. “I want to do whatever I can to help the team out, so if that’s shutting down their No. 1 receiver or their go-to guy, I mean, that’s my job.”

Williams, who’s still sidelined by the knee injury suffered against the Texans, isn’t a lock to regain the starting position when he does return, because Leodis McKelvin has played well in his place.

“He’s had a couple issues with penalties here or there, but for the most part he’s really been on top of his game out there at corner,” Gailey said of McKelvin.

“It’s been fun to watch to be honest with you. He’s done a good job. ... When Aaron gets back, I don’t know exactly what’s going to happen.”

Gilmore, though, is still expected to guard the other team’s No. 1 when Williams does get back.

“I think a lot of that will still continue,” Gailey said. ”

Gilmore hasn’t given up a passing touchdown since Week Five in San Francisco. But that’s not to say he’s been perfect. He’s particularly struggled at times with double moves.

“Sometimes you get your eyes in the backfield. You’ve got to pick and choose the times to make that decision,” he said.

“When I’m guarding a receiver, I’ve got to break to him, almost to the last second. Sometimes in college you can get your eyes in the backfield and they’ll throw the ball right to you. It’s not like that. You’ve got to keep your eyes on the receiver. I’m learning still. Me keeping my eyes on his hips, so whenever he breaks, I’m breaking toward him.”

Gilmore plays a physical brand of football, sometimes too much so.

He’s been flagged for seven penalties, including three in a Week 10 loss at New England, one of which was a questionable pass interference in the end zone that set the Patriots up for an easy touchdown.

He’s also still looking for his first career interception.

“It’s going to come. I’m not really stressing about it,” he said. “I’m making plays, so being physical, it’s going to come.”

Gilmore forced a fumble Thursday against the Dolphins when he stripped Hartline. Bills safety Jairus Byrd recovered, setting up a Buffalo field goal.

“I definitely feel like I adjusted. It feels like college again,” Gilmore said. “I’m out here playing, having fun, doing what I’ve been doing my whole life.”

Now 10 games into his rookie season, Gailey said that experience is starting to show.

He’s closer to being a second-year player than he is a first-year player,” the coach said. “Those guys [Gilmore and second-round pick Cordy Glenn] are becoming more and more mature as they play and are learning every week.”