New England Patriots wide receiver A.J. Brown, who left Wednesday night's loss to the Seattle Seahawks because of an injury, is believed to have suffered a high ankle sprain, sources told NFL Network's Ian Rapoport and Mike Garafolo.
X-rays did not reveal a fracture. Brown has an MRI scheduled for Thursday to determine how much time he'll miss.
Patriots coach Mike Vrabel wouldn't confirm Thursday that Brown has a high ankle sprain but said the team was running more tests on the star wide receiver's injury.
"I don't know if he'll be available going forward here for the next week, but we'll see," Vrabel said. "I know he'll do everything that he can to get back as quickly as possible and once we get the reports then we'll figure out what the treatment plan is."
Brown left the game against the Seahawks early in the third quarter of New England's 13-10 loss.
Brown, in his Patriots debut, remained down after a third-down incomplete pass in which quarterback Drake Maye was throwing in his direction with Seahawks cornerback Nehemiah Pritchett in tight coverage. Pritchett's right knee appeared to land on Brown's ankle with the force of his body weight. Brown grabbed for the back of his right leg as he sat up.
He slowly walked to the sideline, going to the medical tent for an extended period. He then walked to the locker room with members of the athletic training and medical staff.
The Patriots traded a 2028 first-round pick and 2027 fifth-round pick to acquire Brown from the Philadelphia Eagles on June 1.
Earlier in the game, Brown helped set up the Patriots' first touchdown by coming back for an underthrown Maye deep ball and drawing a defensive pass interference penalty. Maye hit rookie tight end Eli Raridon for a 2-yard touchdown on the next play.
The Patriots have an extended layoff until their Week 2 game, next playing the Steelers at home Sept. 20.
ESPN's Mike Reiss contributed to this report.