The Miami Heat’s scintillating showing from 3-point range was the primary reason the Celtics were upset in Game 2 of their first-round playoff series.

But it didn’t help that one of Boston’s most important players turned in the worst performance of his C’s tenure.

Center Kristaps Porzingis was a nonfactor in Wednesday night’s 111-101 loss at TD Garden, scoring just six points on 1-of-9 shooting against Miami’s physical and aggressive defense. His 11.1% field-goal percentage was by far his lowest of the season. Porzingis also missed all four of his 3-point attempts after going 4-for-8 from deep in Game 1, which the Celtics won comfortably.

“They did a hell of a job, to be honest,” Porzingis said after Thursday’s practice at the Auerbach Center. “And I didn’t have a good offensive game at all.”

Porzingis, who averaged 20.1 points per game during the regular season, believes a few minor tweaks will yield better results in Game 3, which tips off at 6 p.m. ET on Saturday in Miami.

“I think them being extra — extra swiping of the ball, being handsy and gambling on some of those possessions — worked out for them,” he said. “It’s small margins. Us getting a little bit better position, little bit cleaner look at the pass, little bit better positioning, it makes a big difference.”

Even getting the ball in Porzingis’ hands proved difficult for Boston. Several attempts to feed the 7-footer down low resulted in turnovers. The Celtics were outscored by 32 points over Porzingis’ 30 minutes, the 28-year-old’s worst plus/minus rating since January 2018.

“Every layer of that has to be better,” Celtics coach Joe Mazzulla said. “The initial screen has to be better. The seal has to be better. Catching the pass closer to the scoring area has to be better. The pass has to be better. Just those things, they test your discipline to be better at all those little things.”

Porzingis wouldn’t reveal specific adjustments he plans to make in Game 3 but said he’s confident he’ll be able to adjust to Miami’s defensive tenacity. Fellow big Al Horford concurred.

“KP will be fine,” Horford said. “… He missed a lot of touch shots that he normally makes. That’s bound to happen. I’m confident he’ll be good to go on Saturday and he’ll be much better.”

Boston also will need more from the rest of its supporting cast. Players not named Jaylen Brown (33 points) and Jayson Tatum (28) combined to score just 40 points in Game 2.

Defending from deep a clear emphasis

Playing without injured starters Jimmy Butler and Terry Rozier, the Heat adopted a bombs-away approach against the more talented Celtics in Game 2, and it worked.

Miami’s 23 made threes Wednesday night set a franchise playoff record, and its 53.5% success rate on those shots far outpaced the Heat’s regular-season average of 37.0%. Boston, which sank 22 triples in Game 1, held a three-point lead at halftime but couldn’t keep pace as the eighth-seeded Heat evened the best-of-seven series 1-1.

All but six of Miami’s 43 3-point attempts were “open” or “wide open,” according to NBA tracking data, with the Celtics often favoring soft closeouts against Heat players whom, in Brown’s words, they “normally would feel comfortable” letting shoot. That strategy backfired, as six different Miami shooters made multiple treys in the win.

“We have to make the adjustment,” Mazzulla said. “… Better closeouts, take away the (threes) in transition. I think we gave up four or five open ones in transition. And then reading their drives. … It’s definitely a test of that, and we can definitely be better at that end of the floor.”

Hoping you hit more than 50% of your 3-pointers should be an unsustainable blueprint for success in the NBA, but the Heat have been able to rattle off four such outings against the Celtics in the last two postseasons. Ensuring they don’t see a fifth Saturday night will be Boston’s top priority as the series shifts to South Beach.

Latest on Kornet

Mazzulla offered an update on reserve center Luke Kornet, who missed Games 1 and 2 with a calf strain.

“He’s doing good,” the coach said. “He came down on the court a little bit today, so we’ll find out more tomorrow how he kind of responds to that.”

Kornet averaged 15.6 minutes per game across 63 regular-season appearances as a frontcourt option behind Porzingis and Horford. With the 28-year-old unavailable, Boston utilized an eight-man rotation in each of its first two playoff games, with only Horford, Sam Hauser and Payton Pritchard seeing minutes off the bench.