Gordon Hayward was taken out of the Boston Celtics' NBA season opener against the Cleveland Cavaliers with what appeared to be a serious leg injury.
Hayward jumped in an effort to catch a pass from a team-mate when he came down on his ankle on Tuesday.
The 27-year-old appeared to have broken his leg, which was put in an air cast as he was taken off the court on a stretcher.
Hayward was picked up in free agency this offseason by the Celtics.
He signed a four-year, $127million contract. Hayward had two points and a rebound at the time of his injury.