LAKE BUENA VISTA, Fla. -- The Boston Celtics lost forward Gordon Hayward to a right ankle sprain in the fourth quarter of their 109-101 victory over the Philadelphia 76ers.

"Sprained ankle," Celtics coach Brad Stevens said afterward. "Don't know the severity, but he's clearly in pain, and it looked like it had some swelling already. That's my medical review."

Sources told ESPN's Adrian Wojnarowski and Malika Andrews after the game that Hayward would be getting an MRI on his ankle later Monday to determine the severity of the injury.

Hayward, who scored 12 points on 5-for-14 shooting with four rebounds, three assists and four steals in 34 minutes, was trying to box out Sixers star Joel Embiid inside with about three and a half minutes to go in the fourth quarter when his right foot got twisted and he went down to the floor in a heap. Boston eventually had to commit a take foul and then call a timeout with 3:08 remaining in the fourth to allow Hayward, who never got off the ground, to slowly limp along the sideline and directly back to Boston's locker room.

Already a thin team as it is, the Celtics will struggle to replace Hayward if he has to miss a significant amount of time. While Boston played 11 players Monday, five of them -- Hayward, Jaylen Brown, Jayson Tatum, Kemba Walker and Marcus Smart -- played more than 30 minutes, and center Daniel Theis (25 minutes) was the only other one who played more than 13.

If Hayward does have to miss time, Smart would all but certainly slide into his place in the starting lineup.

This ankle is the opposite one from when Hayward suffered a gruesome leg and ankle injury in the opening minutes of his first game as a member of the Celtics in 2017, forcing him to miss the remainder of that season. This year, Hayward bounced back to the form he showed before the injury as a member of the Utah Jazz, averaging 17.5 points, 6.7 rebounds and 4.1 assists while shooting 50 percent from the field and 38 percent from 3-point range.

Hayward has a player option on his contract for next season.