Allen started his third season at right guard at Pittsburgh and helped Dallas gain 380 total yards, including 295 passing yards, while not allowing a sack. He left the September 15 win over the Philadelphia Eagles after suffering a strained left hamstring in the second quarter and did not return. Allen returned to the starting lineup following the bye week, against the Chicago Bears on September 28, but was forced to leave in the second quarter without enough strength in his left leg to block effectively. He was once again back in the starting lineup the following week at the Giants. Allen was then forced to move out to left tackle after the loss of Tuinei during a game at Washington on October 13. Allen remained at left tackle in third down passing situations against the Eagles and Redskins on October 26 and November 16. He became a full-time starter at left tackle against the upstart Carolina Panthers on December 8, and remained there the final three weeks of the season.