BOSTON -- The New York Knicks and Boston Celtics were both missing key starters for Sunday night's Atlantic Division showdown, as Knicks guard Jalen Brunson (sore left foot) and Celtics center Robert Williams III (left hamstring tightness) sat out.

Brunson, according to Knicks coach Tom Thibodeau, woke up with soreness in the foot and will be reevaluated Monday.

"Just next guy get in there," Thibodeau said when asked how the Knicks will manage without their star point guard. "I love our depth. The thing you're weighing is, do you want to disrupt what you have going with your second unit?"

Immanuel Quickley replaced Brunson in the Knicks' starting lineup Sunday.

Thibodeau wasn't sure if Brunson would require more testing, saying only that he's day-to-day.

"They're looking at it," Thibodeau said, referring to New York's medical staff. "I don't think it's anything serious. He just woke up with soreness. So we want to make sure he's good."

As for Williams, Celtics coach Joe Mazzulla said the team's starting center will be sidelined the next seven to 10 days after he grabbed at his left hamstring midway through the third quarter of Friday's loss to the Brooklyn Nets, a game Boston led by as many as 28 points in the first half.

Williams has played in only 28 games, having missed the first two months of the season after undergoing knee surgery just before training camp.

"He's done a good job of his rehab and coming back and working through stuff," Mazzulla said. "So, we're not going to rush him by any means. But when he's healthy we need him and we want to play him. So, whenever he comes back, we'll be ready."

Williams sitting out will continue a season-long trend for Boston of not having its expected starting lineup available. Through the first 65 games, including Sunday night's matchup against New York, Boston has had its core starting group -- Williams, Al Horford, Marcus Smart, Jaylen Brown and Jayson Tatum -- available for only 10 of them.

In addition to Williams, Boston was without guard Malcolm Brogdon for the second straight game because of right ankle soreness.