We watched film of Game 1 with Marcus Smart. He explained what makes him a defensive menace.

On Monday, Marcus Smart became the first guard to be named the NBA’s Defensive Player of the Year since Gary Payton in 1996.

On Tuesday, the Celtics veteran sat down with the Globe and provided a look behind the curtain that showed how he operates, as he dissected five of his key defensive plays in the 115-114 win over the Nets in Game 1.

1. Contests Kevin Durant’s drive to the rim (3:04, second quarter)

Smart is serving as a weak-side help defender on Goran Dragic when he sees Durant blitz past Jayson Tatum with a clear path to the rim. Smart’s decision was easy.

“Nothing against Dragic, but it was KD to the rim wide open or Dragic with a three,” he said. “I’m taking my chances, and I’m picking KD. I know I’m probably not going to block his shot, but I’ve got a little bit of weight on him. So just jump vertical and try to make him finish through me. And that’s what I did. Hands went up — you could see they’re complaining about the no-call, but it was clear as day a good read and good play.”

Smart stayed vertical, met Durant in midair, took a bump, and forced a tough shot that missed. Smart said the key to these plays is timing.

“I jump after KD jumps,” Smart said. “He plants and takes off, and as he’s coming down, that’s when I take off. This is how I always think when I go up to contest a shot. They have to come back down to score. So you just put your hands up and stay around the cylinder. Hopefully the ball reaches your hands or you make a play like this.”

But new challenges can arise while in midair. When the oncoming player initiates contact, it can be challenging for the defender to keep his arms held high.

“You get hit, and it makes your arms come down a little, and then the ref sees you’re not vertical and calls a foul,” Smart said. “So knowing that, when I get hit I exaggerate and make sure my hands are even further back, and I tighten up my abs and brace for the hit, like a boxer.”

2. Steals Kyrie Irving’s baseline inbounds pass (10:06, third)

Smart is always wary of teams trying to catch the Celtics’ defense sleeping after a made shot. So he often lurks in the backcourt when the opponent prepares to inbound the ball, just to briefly slow their counterattack. That was his primary goal at this moment.

But as Smart stood near the 3-point arc with his back to Irving, the inbounder, he noticed that the other four Nets had crossed midcourt. Irving’s five-second clock to pass the ball in had started ticking, and he was suddenly on an island.

“So now, I turn into a free safety,” Smart said. “I see those four players, and I know Kyrie can’t just throw the ball to himself. So I’m like, ‘Oh, crap.’ So I turned around to face Kyrie and see where his eyes were going to try to read him. And at this point, he’s in a pressure situation. His five-second clock is going. He has to get the ball in. His teammates are scattered and in chaos mode trying to come back to help him, so he has to throw it in and it’s going to be a hectic pass.”

Brooklyn’s Bruce Brown and Seth Curry streaked up the right side to give Irving an outlet, but their proximity made Smart’s decision even easier. He read the pass, scooped up the ball, and soared for a dunk.

“At that point it was just reading his eyes and making a play,” Smart said. “Where he was standing, that was a long pass, which gave me enough time to get there and just be me.”

3. On-ball defense against Irving (0:30, fourth)

Thirty seconds earlier, Irving shook Smart with a step-back move and drilled a 28-foot 3-pointer to give Brooklyn a 114-111 lead, and Smart was still fuming over what he viewed as a mistake.

“I was pretty down on myself because for me, playing Kyrie and how hot he got, you’ve got to know that that’s coming,” Smart said. “Every aspect of his game is on display with the ball in his hands. The spin, the dribble, the bump-off, the give-back, the hesitation, beating the trap. It’s all there. For me it’s just, stay in front and do everything you can. If he makes the shot, at least make it tough.”

Smart picked up Irving about 10 feet beyond the 3-point line, crouched in his stance, and dug in.

“All I was thinking about was, ‘OK, it’s just me and you. Here we go. Let’s see it,’ ” Smart said. “It was just me and Kyrie in the gym at this moment. Then Al [Horford] comes over and I’m like, ‘Oh, crap. I have help now. I can be even more aggressive.’ ”

Smart gave Irving a slight bump before Horford arrived, and then the two hounded him for several seconds as he tried to find open space in the paint. After 13 dribbles, they eventually trapped Irving near the right corner and forced him to pass the ball to Durant, whose 3-pointer missed.

“It ended up working,” Smart said,

4. Takes a charge against Nic Claxton (4:30, second)

Durant was probing near the top of the key when Claxton came up for a pick-and-roll. Smart was guarding Brown, a solid but not especially dangerous 3-point shooter, who was standing in the right corner.

“Brown is a lesser threat than KD, or Claxton rolling to the rim,” Smart said. “So you’ve got to pick your poison. If Claxton would’ve got to the rim, it would’ve been an easier shot, a layup. So we take away the easiest shot, and I just happened to be in the right spot.”

Smart has turned drawing charges into an art. He takes great pride in getting into the right spot at the right time and putting his body on the line for a looming collision.

“You have to make sure you know where you are on the floor,” he said. “Make sure you’re not in the restricted area, and also make sure you take the charge in the chest and not on the side, where they might call a block. You have to take it. You can’t run from it. If you fall early, it’s a block. If you turn, it’s a block. So you have to really take it.”

Smart stood his ground, absorbed the contact, and got the call.

“For me, it was just protecting our rim and protecting our basket,” he said. “I’m not [Celtics center Robert Williams]. I’m not 6-10 jumping out of the gym. So, for me, it’s taking the charges and putting risk on my body that way.”

5. Steals ball from Durant (5:10, first)

On defense, Smart’s eyes constantly dart around the court, searching for the next opportunity that might not have anything to do with the action transpiring near him.

In this case, Brown was once again camped out in the corner and Durant was looking for an opportunity. Grant Williams did well to keep Durant in front of him and disrupt his drive, and a slight stumble was all Smart needed to see.

“It’s just making a read from there, making a play on the ball,” he said. “They give me a lot of opportunity to play that free safety role and just make a play and use my instincts.”

But not all of Smart’s steals are works of art. Here, he knocks the ball away and stumbles a bit, because he is thinking about what comes next.

“You can see, the reason I don’t get the ball at first is because I’m already looking up the floor,” he said. “I’m trying to look up so as soon as I get it I can head upcourt and see what we can get. I’m always trying to turn defensive plays like these into transition opportunities as quick as I can.”

But when there is a loose ball, he is usually the one to gobble it up. And that’s what happened.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him @adamhimmelsbach.