Jaylen Brown, who missed Sunday’s loss to Cleveland due to a non-COVID illness, led the Celtics with 29 points. However, it was one of those nights where Jayson Tatum probably needed some time off. But that’s not his style. He was listed as questionable with right patella tendonitis, but there was no doubt he would play.

Unlike many of his NBA peers, Tatum prides himself on playing every night. But there are situations where Tatum needs saving from himself.

He finished the game with 18 points on 7-for-21 shooting and six turnovers. He missed nine of his 12 3-point attempts. Five of his turnovers came within eight minutes of the third quarter.

He fought against himself and his tiredness. And even though he’s only 26 years old, Tatum is vulnerable to the rigors of an NBA season.

“The boys are proud to play,” Mazzulla said. “(Tatum) has a great camp around him where they just do a great job taking care of his body. You need people who are proud to play and it won’t be pretty every night, but it’s more about the preparation.

“You see that in Jayson and what Jaylen did to prepare for tonight’s game. It is important. It sets the tone for the guy; it sets the tone for the locker room; It sets the tone that you’re ready to work through the things you want to play. So I would rather they were out there and not looking fresh than if they weren’t out there.”

Before the game, Mazzulla was asked about Tatum’s workload and said he trusts his superstar will decide when he is fit to play. The Celtics suffered a last-minute loss to the Cavaliers and Tatum missed two crucial shots in the final minutes that could have decided the game.

“All of our guys love to play,” Mazzulla said. “If they don’t, it’s because they really can’t.”

There was plenty of motivation for him playing against the Heat, the Celtics’ main rival in the Eastern Conference, and his close friend Bam Adebayo. Speaking of Adebayo, he played worse on Monday against the Celtics than he ever has in his career, even though he’s coming off two games in a row.

He was short-armed jumpers, missed layups and appeared hesitant when facing bigger Luke Kornet or Neemias Queta. He upped his numbers (15 points, 8 rebounds, 5 assists) in a meaningless fourth quarter, but the TD Garden faithful fell far short of Bam Adebayo’s best.

Monday was one of those nights that both franchises point to as they review the newly released schedule knowing that turnover will be an issue. The Celtics played Chicago on Friday and then Cleveland on Sunday. They play the Detroit Pistons on Wednesday before facing the Milwaukee Bucks and Memphis Grizzlies on Friday and Saturday.

These are indeed the dog days. Mazzulla needs to give Al Horford and Kristaps Porzingis the appropriate time off to ensure they are ready and rested for the long haul. Tatum had to shoulder a larger offensive load on Sunday with Brown and Derrick White both sidelined.

Luckily for the Celtics, both returned on Monday and Tatum didn’t have to be the first scorer. The Celtics’ fatigue showed in the second half with 14 of their 17 turnovers. It was a sloppy game with a lot of missed throws, short jumps and bad passes.

But the Celtics survived, cruised to a win, stayed healthy, got players like Drew Peterson and Baylor Scheierman playing time, and now got a much-needed day off.

“It’s part of the journey,” Brown said of the second half of back-to-back games. “One by one, it’s not just the Celtics that have to play them. It’s no different for everyone across the league. I think we try to have the mindset that no matter who is out there, we’re going to come out and play our best basketball.

“That’s part of the adversity. Back to back is difficult to get your body, mind and everything up to speed depending on the flights and the injuries. If you want to do something special, you have to accept these moments. It’s hard for teams to be great when some of their best players never play back-to-back.”

TD Garden saw higher quality basketball than Monday’s Heat-Celtics contest, but irregular games are sometimes part of the NBA experience. Neither team was completely healthy. Neither team played their best game.

But the Celtics have shown that they are better prepared for such situations, and that depth and preparation make them an elite team.

Gary Washburn is a Globe columnist. He can be reached at [email protected]. Follow him @GwashburnGlobe.