The Boston Celtics have been dealt a blow in the NBA playoffs following confirmation of an ankle sprain that will sideline Gordon Hayward for four weeks.

Hayward hurt his ankle during Boston's 109-101 victory over the Philadelphia 76ers in Game 1 of their Eastern Conference first-round series at Walt Disney World Resort on Monday.

The 2017 All-Star, who posted 12 points against the 76ers, twisted his right ankle as he tried to box out Joel Embiid with just over three minutes remaining in the fourth quarter.

Now, Hayward is set for an extended stint on the sidelines in Orlando, Florida, after being diagnosed with a grade three ankle sprain.

"I think we can certainly do a lot here but all that is stuff is to be determined," Celtics head coach Brad Stevens said on Tuesday as he discussed how Boston would adjust in the forward's absence. "We haven't gotten into that stuff or that conversation."

"He's bummed, as you can imagine," Stevens said. "[He's] put in a lot of time and effort, and you do so for this time, for the playoffs. That's what we all look forward to, and we've been really lucky thus far in the bubble to have good health and, of course, [after] Game 1 we don't.

"But that's part of it. We've lived this before and we're going to have to have other people step up. That's why you have a team."

Hayward, who suffered a gruesome leg injury in 2017, has been averaging 17.5 points, 6.7 rebounds and 4.1 assists for the Celtics this season.

Game 2 between the Celtics and 76ers will take place on Wednesday.