Thomas will undergo more tests Monday after Washington returns home.
Losing Thomas would be a big blow to Washington, which is now 6-6 and two games behind first-place Dallas in the NFC East. The WFT currently holds the sixth playoff spot in the NFC with five games remaining.
Thomas was hurt with 10 minutes remaining in the game when he pulled to the left side and was hit low in the left knee by Las Vegas defensive end Yannick Ngakoue. Thomas left on his own power. Washington coach Ron Rivera said in his postgame news conference that he did not see the play.
Thomas has been Washington's top red zone target and its most productive tight end in that area over the past two years. He entered Sunday leading all tight ends with 144 receiving yards in the red zone over the past two seasons -- despite missing six games this season with a hamstring injury.
On Sunday, he showed his worth in that area when he made a leaping one-handed grab in the back of the end zone for a 7-yard touchdown. He caught three passes for 48 yards. In six games this season, Thomas caught 14 passes for 148 yards and two touchdowns.
Washington signed Thomas to a three-year contract extension worth up to $24.05 million in August. That came after his breakout 2020 season, when he caught 72 passes for 670 yards and six touchdowns to establish himself as a pivotal player within Washington's offense.
Without Thomas, Washington will have to rely on Ricky Seals-Jones, who has missed the past three games with a hip injury but was able to return to practice last week, albeit in a limited fashion. He was inactive Sunday because of the injury. The WFT also has rookie John Bates and Sammis Reyes.
In the five games Seals-Jones played after Thomas was hurt, he caught a combined 20 passes for 192 yards and a touchdown. For the season, he has 23 catches for 230 yards and two scores. Bates is primarily a blocker, but he has caught nine passes for 74 yards this season.
Washington has been banged up lately yet continues to win. Sunday, it played without running back J.D. McKissic (concussion) and safety/linebacker Landon Collins (foot). Defensive end Chase Young is out for the year with a torn ACL, and fellow end Montez Sweat has not played during the four-game streak because of a jaw injury. The team started its fourth center, Keith Ismael, on Sunday.