BOSTON -- The Celtics announced Monday night that Gordon Hayward will be out six weeks following successful surgery to repair a broken fourth metacarpal bone in his left hand.

Hayward had the surgery in New York on Monday afternoon, after suffering the injury late in the first half of Saturday's 135-115 Celtics win over the Spurs in San Antonio.

"I feel bad for anybody that goes through that," Celtics coach Brad Stevens said before Monday's game about Hayward's injury. "But this is ... I said this the other day, this is not two years ago.

"He'll be out for a little bit and hopefully surgery goes great and then we'll figure out when he can come back. The silver lining, any time you miss games, is that you're more fresh at the end. At the end of the day he was playing great, but we've got other guys that are ready to step up and fill the void."

Marcus Smart took Hayward's place in the starting lineup for Monday night's game against the Dallas Mavericks at TD Garden, with the Celtics announcing the result of Hayward's surgery late in the first quarter.

Hayward suffered the injury when he collided with Spurs forward LaMarcus Aldridge when the latter was setting a screen on him that he didn't see coming. While Aldridge was called for an offensive foul on the play, Hayward -- whose left arm got caught between his body and Aldridge's -- immediately began shaking his hand, and went straight back to Boston's locker room. An X-ray later revealed the break.

The nine-year veteran 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's been repeatedly praised by scouts who've seen him play in the early going, and has benefited from an offseason fully dedicated to working on his body and game, rather than rehabbing like he did last summer.

Hayward missed all but six minutes of his first season with the Celtics following gruesome leg and ankle injuries he suffered in the opening game of the 2017-18 season, and often looked tentative last season as he slowly made his way back.

But after Hayward spent the summer living in Boston and working out at the team's facility, the Celtics privately were excited about his progress -- excitement he proved to be legitimate as he has been Boston's most consistent player so far this season. Now Boston will have to lean more heavily on its other three perimeter scoring threats -- Kemba Walker, Jayson Tatum and Jaylen Brown -- to pick up the slack left by Hayward's absence.

"It's going to be tough because he was playing great, and we were playing great as a team," Tatum said after the team's shootaround Monday morning. "But, just next-man-up mentality. Next guy has to be ready."

Also helping to soften the blow of Hayward's injury was the return of Enes Kanter, who had been out since suffering a left knee contusion in a collision with Philadelphia 76ers star Joel Embiid in the third quarter of Boston's season-opening loss in Philadelphia. Kanter checked into a game for the first time in Boston late in the first quarter, and received a nice ovation.