The X-factor: Bills running back LeSean McCoy

Buffalo running back LeSean “Shady” McCoy is off to a slow start.

The five-time Pro Bowler turned 29 and is inching closer to the magic number of 30, which signals a natural biological downward turn for most NFL running backs.

He has rushed 48 times for 140 yards for a very un-Shady like 2.9 yards per carry. He also caught 18 passes for 131 yards in the Bills’ first three games. Buffalo is 2-1 and set to face the Falcons.

“LeSean is a big weapon for us coming out of the backfield from a running standpoint, so I think we’ve done some good things,” Buffalo coach Sean McDermott said. “We have to continue to improve. Which is what I’m looking forward to.”

The Falcons haven’t notice any slippage by McCoy.

“He looks impressive to me,” Falcons defensive tackle Grady Jarrett said. “He looks fast, quick and strong. It doesn’t take nothing, but a blowout game to elevate yourself. Numbers can be misleading sometimes.

“He definitely looks explosive and fast.”

McCoy has rushed for more than 1,000 yards five times, including 1,267 yards last season.

“McCoy, I think ... there are some concepts in their system that are similar to ours,” Falcons coach Dan Quinn said. “The wide-zone with the play-action and the keepers that go along with that.”

The Falcons held the Lions to 71 yards rushing. They are giving up 85 yards rushing per game, which ranks ninth in the league.

The Falcons are bracing for McCoy’s cutback runs.

“It just seems like forever he’s been effective in the passing game, fantastic in the screen game,” Quinn said. “They’re committed in the run game.”