The Celtics beat the Rockets by 32 points last Saturday, but Joe Mazzulla didn’t put much stock in that win.

The name Mazzulla gave it was “fool’s gold.” He knew that the Rockets got to Boston late after a tough back-to-back road trip. He knew that night the Celtics made 24 three-pointers. He thought it would be a lot more like the game that happened in Houston on Sunday, where the Rockets used their strong defense to make it more physical and close.

The Celtics did have more problems on Sunday, even though the Rockets were playing the second half of a back-to-back and were missing star guard Fred VanVleet. Most likely more than they should have. In the third quarter, they had more trouble. Jayson Tatum had more trouble. But for Mazzulla, this was another game to show how much they’ve grown and how they can win games even when they’re not playing their best.

Kristaps Porzingis was great on both ends of the court. He scored 32 points, including six 3-pointers and some big buckets near the end of the game, and blocked five shots. The Celtics beat the Rockets badly on the offensive glass and had more second-chance points than any other team. While Al Horford and Jrue Holiday were out, Mazzulla loved how his bench stepped up again. The Celtics won 116–107, even though it was tougher than it should have been.

The Celtics didn’t shoot the ball very well. Tatum, in particular, only made 4 of 17 shots. Tatum and Jaylen Brown were able to score easily last Saturday, but Ime Udoka didn’t seem willing to let them do that again. But the Celtics had Porzingis ready as a surprise. He looked for mismatches and punished the Rockets when they put smaller players on him. The C’s had 23 second-chance points to 10 for the other team’s. Their attack slowed down in the second half, but their defense came through when it counted to seal the win.

“I think that’s the recipe. One thing we learned from last year is that we need a different switch-attack when we’re not shooting well.” Reporters in Houston asked Mazzulla about it. “That’s what Kristaps brings to the post, and our offensive rebounding and crashing is how we fight for extra possessions.” This year, we stress it a lot.”

The Celtics got back on track after losing to the Nuggets on Friday, with Jaylen Brown recording his third career triple-double with 13 points, 11 rebounds, and 10 assists. This is another example of how tough they are. After losing, they’re now 9-1 and haven’t lost back-to-back games since November 6 and 8.

“We know that we can’t lose several games in a row if we want to be a championship-caliber team,” Porzingis told Abby Chin of NBC Sports Boston.

That’s for sure—they didn’t help things along. With a 15-point lead at the break, the Celtics were in charge of the first half thanks to extra work on the glass and strong play from their bench. But they were too flat in the third quarter, which has happened too many times this season. In the first few minutes, the Rockets cut the Celtics’ lead to nine points. The Celtics answered with an 8-0 run to get back ahead by seventeen points, but the Rockets calmed down again.

The Celtics didn’t score for more than four minutes, and the Rockets paid them for it. Through a 14-2 run, Aaron Holiday scored three points, cutting Boston’s lead to five points. The Celtics missed a lot of shots and turned the ball over too easily, which helped the Rockets score quickly. Early in the fourth quarter, the Celtics pushed their lead back to 11. However, Dillon Brooks led an 8-0 run that cut the Celtics’ lead to three.

The Celtics won in the end, but they missed a chance for their starters to get extra rest before Monday’s tough back-to-back game in Dallas against the well-rested Mavericks, who haven’t played since January 17. Their continued problems in the third quarter were a reminder of a big problem that needs to be fixed before the playoffs.

However, the Celtics’ strong finish with their double-big group that included Luke Kornet was a bright spot in their rough play. With 8:22 left, they were ahead 93–90 when Kornet blocked Brooks hard. The C’s got back on track after Mazzulla called a break. The C’s went back up eight points with a 3-pointer by Payton Pritchard after another block by the Knicks.

The Rockets fought back, but in the end, the Celtics buried them with Porzingis. With 3:33 left, he made two shots to give them a 107-96 lead. Holiday replied with a three-pointer, and Brown then missed two free throws. But they kept the Rockets from getting close. Before Porzingis’ fifth block with 2:01 left, Kornet made a tip-in, which pretty much sealed the win.

With their pressure and tricky moving defense, Udoka’s Rockets made it hard for the Celtics to score in the second half. In the end, though, Porzingis made the difference.

“I think that we need to keep working on being able to play out of the post for the long-term success of our team,” Mazzulla said. “So, I believed he was great. He played a great game tonight, in my opinion.