Brown scored 33 points to go along with 11 rebounds while Pritchard, coming off the bench for the first time all year, added 26 points with 7 assists as the Celtics led for the final 37:10.

After the game, Pritchard and Brown each offered their fondness for Simons during his short tenure in Boston.

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“I love Ant,” Pritchard said. “When you build a bond with a teammate, it’s tough to see him leave, Al Horford, Jrue Holiday, Luke [Kornet], KP [Kristaps Porzingis] and now Anfernee. You definitely miss them, but it’s part of the business. So you wish them well and when you see them you got to go at them.”

Simons’s absence impacted Pritchard the most because he’s now likely to come off the bench. He said he had no issue with coach Joe Mazzulla’s decision and it was a comfortable place to return as the reigning Sixth Man of the Year.

“Real simple, we know it benefits our team more, puts another ball handler off the bench,” Pritchard said. “It’s about do you play starter minutes? Do you finish games? I don’t really care about starting. If you want me to start, I’ll start. If you want me to come off the bench, it doesn’t matter.”

Pritchard played 34 minutes and was 12 for 20 from the field and 10 of 12 on 2-point shots as he used his savvy and array of moves to create short jumpers. Brown led the Celtics as he faced off one-on-one against Flagg on several occasions.

Brown said he had nothing but regard for the departed Simons.

“Anfernee has all the respect in the world from me,” he said. “It’s a business, but there’s a human aspect to it. Since he’s been here, he’s contributed to winning, he’s won us some games. He’s a great person, on and off the floor. Just humble. I hope he gets everything he’s looking for.”

Flagg, the Rookie of the Year favorite, led the Mavericks with a game-high 36 points on 12-for-24 shooting and reached the free throw line 12 times. With the likes of Kyrie Irving, Anthony Davis and PJ Washington out with injury, Flagg was a one-man team at times. Dallas’ next-highest scorer was Caleb Martin with 13 points.

The Celtics moved Simons for center Nikola Vucevic but the deal is not likely to be official until Thursday. Boston still managed to shoot 49 percent with Luka Garza scoring 16 off the bench, hitting 4 of 4 from 3-point range.

It took until the second half for the Celtics to consistently sink 3-pointers and the long-range shot allowed them to build a comfortable lead after the Mavericks drew to within 54-48.

Sam Hauser and Baylor Scheierman hit consecutive triples to increase the lead to 11, 64-53. After Flagg hit three free throws to bring the Mavericks to within single digits, 72-63, the Celtics ended the quarter on a 14-4 run. Garza knocked down three 3-pointers in the final 3:58 of the period and Derrick White (11 points) snapped a skid with a wide-open corner 3-pointer as the Celtics took an 86-67 lead.

Flagg was aggressive in attacking the rim but the Celtics threw waves of defenders at him, forcing him to pass. He had 21 points after three quarters on 8-for-15 shooting. No other Mavericks scored more than 11 points.

Brown led the Celtics with 25 points and Pritchard added 17. The Celtics were 6 for 12 from the 3-point line.

The Celtics looked to be in full control when they began the second period on an 18-5 run, sparked by Pritchard and a triple from Garza. The lead was 50-34, but suddenly the Celtics went scoreless for 3:05 and managed just one more bucket the rest of the half.

The Mavericks also struggled to score but got a pair of baskets from Flagg to slice halftime deficit to 52-44. After scoring 15 points in the opening period, Brown managed 2 in the second as the Celtics went 8-for-21 shooting with four turnovers.

They were able to respond with a strong second half and grabbed a key road win in the opener of this two-game Texas swing despite a popular teammate moving on.

“It’s just the character of the guys,” Mazzulla said. “Their ability to have an understanding [of the situation]. Their competitiveness and understanding of the process of winning and the awareness of what gives us the best chance to win. It really comes from the locker room.”

Gary Washburn is a Globe columnist. He can be reached at gary.washburn@globe.com. Follow him @GwashburnGlobe.