Boston forward Hayward breaks ankle just minutes into NBA opener

Boston forward Hayward breaks ankle just minutes into NBA opener

In a horrific start to the NBA season, Celtics forward Gordon Hayward has been stretchered off after suffering a horrible ankle break just minutes into his debut for Boston.

With just under seven minutes remaining in the first quarter against the Cleveland Cavaliers, Hayward's leg bent as he landed awkwardly as he went up for an alley-oop pass from Kyrie Irving.

Hayward sat on the court floor, grimacing at his bent ankle as play was halted and teammates and Cleveland players rushed to him, with the shocked crowd watching on in silence.

Cavaliers star LeBron James gave Hayward some words of encouragement as he was stretchered off with his leg in an air cast.

Several Celtics teammates huddled near the bench in prayer.

Irving, who threw the pass, and veteran Marcus Smart were among those visibly distraught at the injury.

Hayward signed a four-year, $US128 million contract in July to make the Celtics the chief competition for the Cavaliers in the Eastern Conference.

The match was billed as a return to the big-game rivalry between James and Irving, but Gordon's injury has instead shocked the NBA.

"After a medical evaluation by Celtics/Cavs medical personnel Gordon Hayward has been diagnosed with a fractured left ankle," the Boston Celtics said on Twitter.

More to come.