Washington Commanders wide receiver Terry McLaurin was carted off the field on Monday due to a left knee injury that coach Dan Quinn said "could be significant."

Following the Commanders' 23-17 defeat against the San Francisco 49ers in Santa Clara, Calif., Quinn acknowledged "there's fear" that the results of additional testing on Tuesday will show a major ailment.

McLaurin was running a pass route to the sideline late in the first quarter, covered by Deommodore Lenoir, when he went down under minimal contact and grabbed at his knee.

He was eventually fitted with an air cast and driven off the field.

McLaurin ended the night with one catch for 27 yards, which helped set up a field goal. In five games this season, he has 15 receptions for 230 yards and one touchdown. He didn't play in the Commanders' Oct. 4 loss against the Indianapolis Colts in London due to a hamstring injury, but he was back the following week to make four catches for 62 yards in a tie against the visiting New York Giants.

The 31-year-old veteran is in his eighth NFL season, all with Washington, which selected him in the third round of the 2019 draft out of Ohio State. In 112 NFL games (all starts), McLaurin has 513 receptions for 7,191 yards and 42 touchdowns.

He is in the first year of a three-year, $96 million contract.

The Commanders (1-4-1) have a bye week before they return to action with another prime-time game on Nov. 1 against the visiting Philadelphia Eagles (2-4).