Hayward had the surgery in New York on Monday afternoon; he suffered the injury in Boston's 135-115 win in San Antonio over the San Antonio Spurs on Saturday night. The Celtics announced the results during the first quarter of their 116-106 win over the Dallas Mavericks at TD Garden.
"We're going to have to pick it up a little bit," said Marcus Smart, who took Hayward's place in Boston's starting lineup Monday night and scored 17 points in 37 minutes. "Just a little bit more, turn up the energy on both ends. Everybody is going to have to step up now.
"We're losing one of our greatest scorers right now, and he's been playing some of the best basketball of his career. For him personally, we feel bad, and also for the team. But this team is really talented, so it gives everybody else opportunities to step up."
That was the case Monday night, as the Celtics were able to get 29 points from Kemba Walker and 25 from Jaylen Brown, which proved to be enough to hold off a 34-point, nine-assist performance from Mavericks star Luka Doncic.
But the Celtics saw some signs of what they'll have to deal with while Hayward is out for the next several weeks. During the minutes in which he typically was serving as the fulcrum of Boston's offense, the starts of the second and fourth quarters, the Celtics struggled -- thanks in no small part to Jayson Tatum's abysmal 1-for-18 performance Monday night. But even if Tatum had been making shots, the Celtics felt the absence of Hayward's shooting and playmaking when Walker wasn't on the court.
"[We have to] find ways to win regardless," Brown said. "The older we get as we go through this process, we're getting older -- me, [Tatum], guys that's been here, Smart. We know how to win, so we've just got to continue to do that, and I think today was a good example of that."
Hayward has been excellent to start the season, averaging 18.9 points, 7.1 rebounds and 4.1 assists in eight games this season for the Celtics while shooting 55.5% overall and 43.3% from 3-point range. He has been repeatedly praised by scouts who have seen him play in the early going, and he has benefited from an offseason fully dedicated to working on his body and game rather than rehabbing like he was last summer.
There was another brief injury scare during the fourth quarter of Monday's game, when Walker -- who scored 24 of his 29 points in the second half -- got hit by Doncic late in the fourth quarter and his neck snapped back, causing him to eventually head to the locker room and sit out the game's final 2:42. But Walker said after the game he just got a stinger and wouldn't be undergoing any more treatment than he normally would following the game.
One positive bit of injury news was the return of Enes Kanter, who played six minutes in the first half Monday night after sitting out the prior seven games with a left knee contusion following a collision with Philadelphia 76ers star Joel Embiid in the third quarter of Boston's season-opening loss in Philadelphia. Both Stevens and Kanter downplayed the significance of his seeing only a few minutes, saying the plan is for him to ease back into action gradually over time.
"I wasn't feeling really good, because I was not at 100 percent game shape," Kanter said, "but it was really good to be out there with my teammates. Got a win ... you definitely miss it a lot."