Boston • The difference between the Jazz and Celtics was pretty apparent and pretty stark on Friday night at TD Garden.

Utah’s second unit was excellent. Boston’s was pretty much nonexistent.

With the Celtics short-handed owing to Jaylen Brown and Gordon Hayward missing the game on account of injury, the Jazz’s superior depth proved its worth, as they rolled to a 99-94 victory.

The win was Utah’s fourth in a row and improved the team’s record to 40-22 on the season.

It was made all the more remarkable by the fact that Donovan Mitchell didn’t reach double-figures in scoring until there were but 9.1 seconds left, and that neither Bojan Bogdanovic or Rudy Gobert got there at all.

With the Jazz struggling early — they trailed 27-16 with 3:38 left in the first period — and their structured rotation about to feature reserves Jordan Clarkson, Joe Ingles, Tony Bradley and Georges Niang playing alongside starting point guard Mike Conley, it was perhaps fair to wonder if the game was about to be decided on the spot.

And so it did, though not in the way the home crowd hoped for.

Suddenly, Boston’s open looks at 3s were more contested, and instead of settling softly into the net, they were clanking off the rim. Meanwhile, on the other end, Conley found Ingles for a 3 of his own, then lofted a lob to Bradley for an alley-oop. Massachusetts native Niang got a pair of runners to go. Conley converted a three-point play. And Clarkson drove the lane for a layup himself.

“I think we just did a great job locking in defensively, really getting stops, and then really pushing the pace and getting out and running,” said Niang. “Once we do that — and share the ball — it’s tough to stop us.”

The Celtics were left wondering what happened.

The answer? Utah’s second unit closed the quarter on a game-changing 14-2 blitz (including the final 11 points) to put the Jazz ahead.

“I think Boston came out hot and it would have been easy to look around and [say], ‘What’s going on?’ And we just stayed in. We kept doing the same things and we did them better,” said coach Quin Snyder. “… We were defending as a team, and then those guys came in and they took it to another level.”

Conley, who spent extended portions of the game with that group, was the best player on the court for most of the night. He finished with 25 points (on 9-for-16 shooting, including 6 of 10 from deep), five assists and three rebounds.

“All those guys that came in — J.C., Joe, Tony, Georges, just play with great energy and great chemistry with one another. And when I’m in there with those guys, whoever has the ball brings it up and we’re just making plays for each other,” Conley said. “Defensively, I thought, was where we really took a jump in that little stretch. We did a good job communicating, making the right reads, rebounding, and getting out and getting easy layups and 3s.”

Meanwhile, Utah’s reserves outscored their Boston counterparts 39-13, led by Clarkson’s 17 off the bench.

Mitchell finished with 11 points — on 3-of-15 shooting, to go along with three turnovers. Bogdanovic had eight points (on 2 for 9) and five turnovers. Gobert totaled nine points and seven rebounds.

Afterward, they expressed how important it was for their teammates to be able to pick them up.

“Big time. They came out and did what they’re supposed to do — guys competed, run the floor, defending,” Mitchell said. “We gave up four points inside the five-minute mark. Just being able to lock in that level of intensity on defense against a team like that is huge. They really lifted us for sure.”