The plan is for Thomas will undergo further testing to confirm the severity of the injury after the team returns to Washington.
Thomas was attempting to make a block when a defender went low on him and hit his knee.
Thomas, 30, is a former fourth-round pick of the Cardinals back in 2014. He lasted just over a year in Arizona before he was waived and later claimed by the Dolphins.
Thomas was in the third year of his four-year, $2,652,092 rookie contract when the Dolphins waived him in 2017 and he was later claimed by the Giants. He had a brief stint with the Lions after he made the decision to convert to tight end and later caught on with the Bills.
Buffalo declined to tender Thomas a restricted offer and he later signed on with the Lions. He signed a one-year deal with Washington in 2020, then signed a three-year, $24 million extension this summer.
In 2021, Thomas appeared in five games for Washington and caught 15 passes for 148 yards and two touchdowns.