After playing most of his regular starters in the Celtics’ first three preseason games, head coach Joe Mazzulla gave his top unit a night off Sunday.

Mazzulla announced in his pregame news conference that Jayson Tatum, Jaylen Brown, Jrue Holiday, Derrick White and Luke Kornet would not play against the Toronto Raptors at TD Garden.

Those five started both of Boston’s games in Abu Dhabi and Saturday night’s 50-point home win over the Philadelphia 76ers.

Veteran center Al Horford also sat Sunday for the fourth consecutive game. Mazzulla plans to give Horford minutes on Tuesday when the Celtics close out their preseason in Toronto.

“He’ll play on Tuesday. He’s good,” Mazzulla said of the 38-year-old, who’s entering his 18th NBA season. “He’s ready to go. He’s ramping up, getting in shape, working hard. He’ll play on Tuesday in Toronto.”

Kristaps Porzingis remained sidelined, as well, as he recovers from offseason leg surgery. Boston’s starting center, who’s watched from the bench in street clothes this preseason, is targeting a December return.

Mazzulla said every other Celtics player would be available Sunday. Several members of that group are battling for rotation roles and roster spots with just over a week remaining before the start of the regular season.

Among those hopefuls: second-year pro Jordan Walsh, first-round rookie Baylor Scheierman and veteran newcomer Lonnie Walker IV, who’s with the Celtics on a training camp tryout deal.

“The message is the same regardless of who’s playing,” Mazzulla said. “We’re going to compete at a high level. We’re going to execute. We’re going to stick to the things and execute our system offensively and defensively and make sure we play with effort. The message is always the same regardless of who’s in, who’s out, and I think that’s a reason why we have the continuity that we do, because of that standard. So it’s the same.”