CLEVELAND --  Boston star forward Gordon Hayward suffered a gruesome injury, dislocating his left ankle and fracturing his left tibia just five minutes into his debut with the Celtics.

Hayward, who signed a four-year, $128 million free agent contract this summer, went up for an alley-oop pass and collided with LeBron James midway through the first quarter. He got his leg twisted underneath him as he came back to the floor. Hayward collapsed under the basket and looked in horror as his left foot was pointing outward.

He put his hands to his face and dropped back to the floor as a hush fell over the sellout crowd inside Quicken Loans Arena.