Midway through the second quarter of the Celtics’ win over the Rockets on Sunday, Joe Mazzulla changed things up a little.

With 6:20 remaining in the first half, Mazzulla subbed out Jayson Tatum. About a minute later, he subbed out Jaylen Brown. The Celtics’ star duo stayed on the bench to end the second quarter, which was unusual. It’s rare that they’re both on the bench together and atypical that they each don’t finish the half.

But with a back-to-back looming on Monday night in Dallas, it’s possible Mazzulla saw it as an opportunity to steal some rest for his stars. With Jrue Holiday (wrist) and Al Horford (rest) sitting out Sunday, the rotations were different, too. But it was also a testament to Mazzulla’s faith in his reserves.

For the final 5:28 of the first half, Mazzulla rolled with a lineup of starters Kristaps Porzingis and Derrick White in addition to Sam Hauser (who started Sunday in place of Holiday), Payton Pritchard and Oshae Brissett. The unit helped the Celtics build their lead from eight to 15 by halftime.

While Porzingis and White took on the scoring load, the bench players were instrumental in the Celtics’ strong first half, which proved critical as the C’s submitted another underwhelming second half. Hauser was a team-best plus-19 in the first half as he produced three 3-pointers and three assists in addition to strong defense. Pritchard added four assists, and hit an impressive 3-pointer at the shot clock buzzer moments after Tatum was subbed out in that second quarter. Both of them played more minutes than Tatum and Brown in the first half. Brissett and Luke Kornet each provided energy throughout the first half, too, to help the Celtics grab an 19-0 edge in second-chance points at the break.

“I think early on we didn’t have our best energy,” Porzingis told reporters in Houston. “It was kind of our talent that was getting us that lead, and I think that’s one thing that Joe is always emphasizing is that no matter if we’re the most talented team in the world, we have to play hard and we have to show up on every possession, and that’s what he was trying to get out of us. I think that’s why he did those subs, and that second unit, Sam, Payton, they came in with great energy, kind of gave us a spark and that was it. That kind of changed a little bit of momentum of the game, went into halftime up 15.

“This is a good game for us to understand that we need to bring that energy every moment. If not, there’s going to be another guy that’s going to come in and bring it, but we need as many people as we can every night.”

After the Celtics let a 17-point lead get sliced to three early in the fourth quarter, another bench player stepped up. Mazzulla substituted Kornet into the game to create a double-big lineup, and he immediately created a spark. He blocked Dillon Brooks at the rim, and moments later, he swatted away another Brooks shot that led to a 3-pointer from Pritchard as the Celtics reclaimed control. Later in the fourth, Kornet’s tip-in helped seal the victory.

In all, the Celtics’ typical reserve players of Hauser, Pritchard, Kornet and Brissett combined to total 32 points, 20 rebounds (9 offensive), 14 assists and five blocks. On a night they were missing two regulars, and Tatum and Brown were struggling from the field as Ime Udoka put pressure on them, the Celtics needed some contributions elsewhere. Their bench stepped up again.

“That’s why you put so much stock into them, that’s why you believe in them,” Mazzulla told reporters in Houston. “They have to help you win games like that. It’s a long year, there’s going to be nights when you’re not at your best, but those guys brought it. So that’s big-time.”