A 33-point outburst from Jayson Tatum and clutch overtime makes by Payton Pritchard helped the Celtics overcome a dreadful start and avoid their second straight home loss Friday night at TD Garden.

Tatum’s turnaround fadeaway with 1:19 remaining in the extra period proved to be the difference in a 108-104 victory over the Brooklyn Nets, who did not trail until the fourth quarter.

The Celtics star added nine rebounds, nine assists, two assists and a block, and his tight defense forced Nets top scorer Cam Thomas (31 points) into a late-game shot-clock violation.

Pritchard scored six of his 20 points in the extra period, including a pair of late free throws that iced the game for Boston. Jrue Holiday added 17 points, and Horford chipped in 13 points and 10 rebounds.

The Celtics secured the win despite making just 26.4% of their 53 3-point attempts, including rough showings from the typically reliable Derrick White (1-for-6) and Sam Hauser (2-for-10). They improved to 8-2 and now will head to Milwaukee for a Sunday afternoon matchup with the Bucks.

With Jaylen Brown, Luke Kornet and Kristaps Porzingis all unavailable due to injury, head coach Joe Mazzulla trotted out a new-look starting five. He gave Xavier Tillman the nod over Neemias Queta, pairing him with fellow big Al Horford to form a lineup that had played just three total minutes together since Boston traded for Tillman in February.

That experiment quickly flopped. Tillman missed three early 3-pointers, and Boston looked disjointed at both ends, allowing Brooklyn to race out to leads of 12-0 and 16-2.

The improvements Tillman showed as a 3-point shooter during the preseason have vanished since the regular season tipped off. The 25-year-old is shooting 21.4% from deep and 26.1% overall. Mazzulla, who kept Tillman on the bench in two of the previous four games, also gave the forward an earful after he passed up an open three — a no-no in the Celtics’ scheme.

Tillman did not leave the bench after his first six-minute shift.

The Celtics stabilized after Mazzulla made his first round of subs at the midway point of the first quarter, inserting Payton Pritchard, Sam Hauser and Queta. A flurry of threes by Tatum and Pritchard and Holiday’s veteran savvy under the basket helped Boston chisel away at the 14-point deficit.

Queta, a bright spot in Wednesday’s loss to Golden State, also added a spark with his rebounding and rim protection. During one sequence late in the first quarter, Tatum bookended two 3-pointers around a Queta block on Jalen Wilson.

A Pritchard three 18 seconds into the second quarter cut Brooklyn’s lead to one, but the Nets maintained a slim advantage. Boston never led in the first half despite getting 14 points from Tatum and 14 more from Pritchard, who went a combined 7-for-12 from beyond the arc.

One reason for that: Nine first-half turnovers, which, fortunately for Boston, led to just seven Brooklyn points. The Celtics trailed 51-49 at halftime.

Boston pulled even twice during the third quarter before Brooklyn rebuilt a seven-point lead. That was followed by a fleeting Tatum takeover — he scored 11 straight Celtics points, with six coming off Nets turnovers — and then a Cameron Johnson three that shifted momentum back to the visitors. A Tatum trey at the third-quarter buzzer missed its mark, and the Nets took a 78-76 lead into the fourth.

Tatum sat for the next five-plus minutes, and the Celtics struggled to generate offense without him, scoring just six points. The Nets also shot poorly during that stretch but feasted on offensive rebounds, grabbing five to Boston’s zero.

The Celtics finally pulled ahead for the first time when Tatum drove for a fast-break dunk off a Holiday outlet pass and Holiday followed with a second-chance bucket after an offensive rebound by Hauser.

After a three from ex-Celtic Denis Schroder put Brooklyn back in front, Hauser — dreadful from 3-point range for most of the night — received a slick feed from a driving Tatum and buried one from the right corner, making it 92-91 Celtics.

A Thomas free throw knotted the score. Then, after consecutive Brooklyn misses and a Celtics timeout, Tatum drove to the basket and threw down an explosive dunk over two Nets defenders. But again, the lead was short-lived. Tatum fouled Johnson on the ensuing possession, and he made both.

Tatum had a chance at a game-winner as time expired, but his isolation 3-pointer over Dorian Finney-Smith didn’t fall, sending the game to overtime.