X-Factor: Run defense has been lacking in all four losses

Dion Sims of the Bears is tackled by Falcons linebacker Deion Jones during the season-opening game Sunday at Chicago's Soldier Field.

Dion Sims of the Bears is tackled by Falcons linebacker Deion Jones during the season-opening game Sunday at Chicago's Soldier Field.

The Falcons’ run defense will be X-factor Sunday night against the Dallas Cowboys, who average 148.1 yards per game and rank second in the NFL.

The Falcons give up 114.5 yards rushing per game, which ranks 18th in the league (in the bottom half).

One of the common denominators in the Falcons’ four losses is that they have given up more than 100 yards rushing in each game. They gave up 201 yards against Carolina, when they failed to defend quarterback Cam Newton on designed running plays. He rushed for 86 yards.

In losses to New England (162 yards), Miami (138 yards) and Buffalo (117 yards), the run defense was lacking.

“I don’t think the scheme would change because the style of what they do is pretty clear,” Falcons coach Dan Quinn said.