Halfway through the season, Leodis McKelvin is leading the NFL in punt returns and is third in the league in returning kickoffs. Sad as it is to contemplate, he's probably the only Bill with a good shot at being named to the Pro Bowl.

But McKelvin doesn't want to talk about the Pro Bowl now. He's more concerned about winning games. Five years into an otherwise disappointing career, he resents the fact that he's come to be defined by his fine work on special teams.

“Of course,” McKelvin said Wednesday. “I'm a cornerback.”

This Sunday in New England, in fact, he'll be a starting cornerback. For the first time this year, and only the second time since early last season, McKelvin will be lining up as the starting left corner when the Bills take on Tom Brady and the high-powered Pats' offense.

McKelvin has been tossed into the fire because of injuries to Aaron Williams and backup Terrence McGee. It's understandable if Bills fans feel a bit of ambivalence about his promotion. Williams has been a wreck at corner in his second pro season. Any change would be welcome at this point.

But turning to McKelvin is like replacing a flat tire with a bald, half-filled spare. You have no choice but to throw it on and hope it holds up until you can find a better option.

There's a reason Williams was ahead of him on the depth chart. McKelvin was the more established failure. The current regime inherited him. They drafted Williams in the second round, as the 34th overall pick of the 2011 draft.

You have to admire McKelvin, for one thing. The guy never loses his confidence. It doesn't matter how many receivers beat him for touchdowns, or how many times he has position and still gets beat. He has unshakable belief and a defensive back's most enduring quality – a short memory.

“Lose confidence?” McKelvin said. “That's something a cornerback isn't supposed to do. Everybody is human. We're all human. Things happen. You get a pass caught on you. You just can't let it bother you. You've got to win the majority of your battles out there on the field.

“I mean, if you're not confident in yourself,” he said, “why should you play this game? I'm very confident in my ability to play, no matter what it is, special teams or defense.”

I imagine Brady and the Pats are feeling fairly confident. The Pats have never lost to the Bills in Gillette Stadium. The Bills haven't won in New England since 2000. The Pats have won the last 12 second meetings between the AFC rivals in-season, outscoring the Bills, 344-99, over those dozen games.

Brady is 19-2 in his career against the Bills. He has thrown for 5,170 yards with 49 touchdowns and 18 interceptions. He's probably not crushed to hear McKelvin will start. Brady might send a limousine to the Bills' team hotel, just to make sure Leodis gets to Gillette on time.

McKelvin hasn't come close to justifying the Bills' decision to make him the 11th overall pick of the 2008 draft, and the first cornerback. He established himself as the starter in 2010, but lost the job to McGee – and then Williams – after playing poorly in the first five games a year ago.

There were questions about McKelvin's future coming into this season. He played well as a nickel in training camp. He lost the job to Justin Rogers after getting torched by the Jets' Jeremy Kerley in the opener.

He had an interception in the fourth quarter against the Browns. But for the most part, he has done his work on special teams. He returned a punt 88 yards for a TD against the Chiefs. He had an 80-yard punt return nullified by a penalty in San Francisco.

At 27 years old, in the final year of a five-year rookie contract that has paid him nearly $20 million, McKelvin knows he has a lot to prove.

“Oh, most definitely,” he said. “Every time you go out on the field, you've got something to prove. You've got something to prove to the guys that you're playing against. You've got something to prove to the guys you're playing with, and to the guys who trusted you to go out and perform.”

More than once, he mentioned “bad breaks” that have gone against him during his time with the Bills. He acts as if losing coverage or having a taller receiver snatch the ball from him in mid-air were mere incidents of misfortune, rather than inferior defensive play on his part.

Fans recollect with an unforgiving clarity. They will remember McKelvin as a gifted athlete who couldn't master the art of pass defense. For all the long returns, it's the one fateful decision they'll remember most, the late fumbled kickoff return that cost the Bills a victory on a Monday night in the 2009 opener in New England.

“You all won't ever let it go,” McKelvin said. “It's something that happened in the past. Just leave it in the past. I'm not worried about it. Hopefully, the people around this area aren't.”

Fair or not, it's the signature moment in McKelvin's career, and one of the jarring memories in the Bills' long run of failure in New England. The TV announcers are bound to cover it at some point Sunday. Bills fans can only hope that McKelvin manages to cover somebody, too.