The Celtics Finally Look Like They Want to Win

Boston Celtics guard Marcus Smart is difficult to miss. His jump shot can be an amusement-park ride. He will try the occasional alley-oop pass from midcourt. He spoke earlier this month about the apparent brutality of a playoff game as a “true dogfight — scratching and clawing, biting, blood, everything.” He dyes his hair green.

It is all part of the colorful package, and, on Thursday night, Smart showcased his role as a defense-minded agent of chaos on the opening possession of Game 5 of the Eastern Conference finals against the Miami Heat.

Smart was defending Jimmy Butler away from the ball, near the top of the perimeter, when Bam Adebayo of the Heat drove to the basket. Smart reached at the ball, stripped it free and dove to collect it near the foul line before shoveling it ahead to Jayson Tatum for a fast-break layup and the game’s first points.

One play does not define anything, of course, especially in a postseason series. But that play — a clean steal before the Heat could even take a shot — seemed to hint at everything that was to come during the Celtics’ 110-97 victory, which extended their season. The Heat lead the series, 3-2. Game 6 is Saturday in Miami.

The Celtics, the No. 2 seed in the East, forced 16 turnovers in Game 5. They threw a full-court press at the Heat coming out of timeouts. They led by as many as 24 points. By the fourth quarter, Heat Coach Erik Spoelstra was pacing in front of the visiting bench with his hands on his hips, and Butler, who finished with just 14 points against a host of defenders, looked weary.

“I wanted to get us going,” said Smart, who checked out of the game to an ovation after scoring 23 points. “I wanted to come in and give my team some energy, especially going against a team like Miami.”

He added: “We did the knocking around tonight.”

The pressure is squarely on the Heat before Game 6. They would certainly welcome the return of Gabe Vincent, their starting point guard, who missed Game 5 with a sprained ankle. But in case anyone thinks they are reeling, Butler offered a Namath-esque guarantee at his postgame news conference.

“We can and we will win this series,” he said. “We’ll just have to close it out at home.”

Not so long ago, the Heat had all the momentum. In fact, early in the third quarter of Game 4 on Tuesday, they seemed to be closing in on a four-game series sweep. There was one possession in that game when three offensive rebounds led to a 3-pointer by Max Strus, pushing Miami’s lead to 9 points in front of a home crowd that was primed to celebrate a trip to the N.B.A. finals.

The Celtics could have crumbled like a sand castle into Biscayne Bay. But a funny thing happened: They promptly went on an 18-0 run. No longer was the Heat’s zone defense such a riddle. No longer were the Celtics’ 3-point shots rimming in and out. And no longer did the outcome of the series appear to be a foregone conclusion after the Celtics’ 116-99 victory, which sent it back to Boston.

Several Celtics mentioned the importance of a team meeting between Games 3 and 4, which happened at a time when nearly everyone outside their locker room figured their season was toast. Coach Joe Mazzulla was fielding questions about whether he had lost his team. Tatum and Jaylen Brown were being scrutinized for their inconsistent play. Broadcasters were cracking jokes about imminent trips to Cancun.

“I mean, Game 3, that was as low as you can be,” Tatum said. “The good part about being that low is that you only can play better. It’s only up from there.”

After Thursday’s win, Mazzulla said one of his assistants had provided valuable perspective.

“The seasons are, like, nine months long, and we just had a bad week,” Mazzulla said. “Sometimes you have a bad week at work. We obviously didn’t pick the best time to have a bad week, but we did, and we’re sticking together and fighting like hell to keep it alive, and the guys are really coming together.”

The Celtics are making a habit of digging holes — they trailed the Philadelphia 76ers, three games to two, in their conference semifinal series — before MacGyvering their way out. Smart acknowledged that the Celtics may have been too lax in how they had approached their series with the eighth-seeded Heat.

“They snuck up on us and got us,” said Smart, who was asked to elaborate. “That’s the thing about sneaking up on somebody: They’re not supposed to know you’re coming. So that’s what happened. We didn’t know. We didn’t see it, and they got us. It wasn’t like we were trying to have that mind-set. It’s part of the game. It’s part of life. It’s part of the roller coaster of playing in the N.B.A.”

Now, the Celtics are halfway toward snapping one of professional sports’ most curious and seemingly shatterproof streaks. No N.B.A. team has ever come back from a 3-0 series deficit. Earlier this week, the Los Angeles Lakers became the 150th team to have tried (briefly) and failed (miserably) when the Denver Nuggets swept them in the Western Conference finals.

As for the Celtics, Smart pumped the brakes on looking beyond Game 6.

“First of all, we have to worry about one — the next game, not two games,” he said.

On Thursday, Smart was a kinetic force. He connected on back-to-back 3-pointers for an early 10-point lead. He started the first half with a steal and punctuated it with one, too, poking the ball away from the Heat’s Caleb Martin. He defended and scored, grimaced and scowled, finishing with five steals while shooting 7 of 12 from the field and 4 of 6 from 3-point range.

“He’s just an emotional key for us,” Mazzulla said. “When he’s locked in and playing both sides of the ball at a different pace, it kind of gives us our identity and our life.”