McLaurin was hurt on a deep pass down the left sideline with 13 minutes remaining in the quarter. He tried to outjump two Dallas defenders for a pass and hit the ground hard.
He stayed down on the field for a minute before slowly getting up and walking to the bench. Shortly thereafter he headed to the locker room.
McLaurin finished with no catches in a game for the first time in his three-year career. He was targeted just four times.
McLaurin is Washington's leading pass-catcher for the season with 61 catches for 808 yards and five touchdowns. If he has to miss time, it would be a crucial blow to Washington's offense for next week's game at Philadelphia.
Washington played without third-down back J.D. McKissic (concussion) the past two games. Tight end Logan Thomas is out for the year with a knee injury. It has also lost three centers to injuries this season.
Adam Humphries is Washington's second-leading receiver with 33 catches.
Meanwhile, quarterback Taylor Heinicke left Sunday's game in the fourth quarter with a knee injury and did not return. He said after the game that his knee was fine and he was more troubled by an injury to his right elbow in the first half. Heinicke said he expects to play next week, but he is expected to undergo an MRI on Monday, per ESPN's Adam Schefter.
Kyle Allen replaced Heinicke and completed 4 of 9 passes for 53 yards.