TORONTO — When the starters were ineffective early, coach Joe Mazzulla had no interest in letting his regulars work out of their doldrums, He opted for his second unit, looking for a spark on the second night of a back-to-back.

Not only did those reserves ignite the Celtics, who were without leading scorer Jaylen Brown, players such as Luka Garza and Hugo Gonzalez made late-game plays to pull away from Toronto for Boston’s second win at Scotiabank Arena in 13 days.

The 112-96 win was satisfying for the Celtics because it occurred on a night when Derrick White mostly struggled, Mazzulla benched Jordan Walsh because of illness and Sam Hauser, starting for Brown, made just two field goals.

Garza, playing his most significant stretch in nearly a month, pitched in with 12 points and 10 rebounds, 9 offensive. Gonzalez, coming off a sparkling performance Friday against Miami, helped out with 10 points and 10 rebounds, including a streaking dunk to cap the fourth-quarter run.

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Payton Pritchard led Boston with 33 points, carrying the Celtics when the Raptors took a 7-point lead midway through the third quarter. White scored 9 consecutive points in the fourth to extend the lead. Brandon Ingram and Sandro Mamukelashvili each scored 24 for Toronto but the Raptors scored just 16 points in the game’s final 13:41.

The Celtics needed Pritchard to carry the offense and he did in the third quarter, keeping Boston close as the Raptors built a lead with 3-point shooting.

The Celtics had no one who adequately defended Brandon Ingram and he poured in 20 points, drawing multiple fouls from Gonzalez, who had issues with the matchup. Toronto’s lead grew to 69-62 after another Sandro Mamukelashvili 3-pointer, his season-high fifth, but Pritchard scored 12 of the Celtics’ final 21 points in the period for an 83-80 lead.

His most impressive play may have been a behind-the-back dribble in traffic and a shuttle pass out to Hauser for a 3-pointer. Pritchard had 27 points in 30 minutes after three periods.

The Celtics led by 13 points at the 7:30 mark of the second quarter when Anfernee Simons collected a steal and fed White for a streaking layup, but he missed. Mamukelashvili countered with a 3-pointer, which sparked a Raptors run that would give them a 51-49 halftime lead.

Boston scored 8 points in the final 7:47 of the second period and none in the final 2:35. The Celtics missed 16 of 22 field goal attempts and 8 of 11 3-pointers. Without Brown, the Celtics starting lineup struggled against their counterparts while Mamukelashvili and Jamal Shead combined for five 3-pointers.

Toronto ended the half on a 23-8 run and White, who tallied 33 points Friday against Miami, was 2-for-12 shooting in the first half with 6 points. Simons led the Celtics with 9 points but on 3 of 9 from the field.

The key play early was a backdoor cut by Toronto’s Ochai Agbaji against a distracted Walsh that promoted an immediate Mazzulla timeout as he sought out Walsh for a stern lecture. It was then that he opted to pull four of his starters besides Pritchard and go with the quartet of Josh Minott, Simons, Gonzalez and Garza.

For Garza, it was his first non-garbage time stint in nearly a month and he delivered a quality stretch, with 6 points and 5 rebounds, all offensive, as the Celtics closed out the first quarter with a 16-0 run.

The defense stifled the Raptors in the early going, using active hands, and help to frustrate Barnes and Ingram. That second unit gave the Celtics a double-digit lead but it wouldn’t last.

▪ Brown was listed as doubtful with a non-COVID illness several hours before tipoff and eventually ruled out, although he did make the trip to Toronto. Mazzulla said Brown had been dealing with an illness prior to Friday’s win over the Miami Heat but still managed to play nearly 35 minutes and score 30 points. It’s the second game Brown has missed this season. He sat out the Dec. 4 blowout win at Washington with a non-COVID illness. Hauser, who nailed five 3-pointers Friday, got the start in place of Brown.

▪ The Raptors were without center Jakob Poeltl, who is experiencing back issues. Poeltl has had great success against the Celtics in past years. Mamukelashvili got the start at center in place of Poeltl.

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