BOSTON -- "[Marcus Smart] is going to be special in this league," Isaiah Thomas said after the Celtics defeated the Hawks 104-95 in Game 4. "He's only 22 years old, so imagine in a few years what he's going to be like." It was easy to imagine Sunday at TD Garden after being tossed into a wormhole and transported into the future to get a glimpse of Smart's transcendent potential.

Smart was Boston's leading scorer in the fourth quarter and overtime, while scoring 20 over the full game. He also took his elite defense to an even higher level. "You give Marcus Smart an assignment, he's probably going to get it done, no matter who he is playing against," Thomas said. "He's a hell of a competitor. And you need lots of guys like that to win in the playoffs. He played an unbelievable game."

Brad Stevens said last year that even though Kyle Korver averages just 13 points per game, you have to treat him like he scores 30 every night -- or else he will.

The Hawks sharpshooter shredded the Celtics in the opening minutes, so Smart's first assignment was to erase Korver.

"Everybody knows what Kyle can do and the way he can do it," Smart detailed after the game. "He can get hot real quickly and my job was to make it tough for him, trail him, just be physical with him, and get into his air space."

Korver didn't attempt a single shot while Smart was his primary defender in the half court. He did shoot 1 of 2 against Smart, but one of those plays came against a scrambling Celtics defense in transition, and the other Smart was an off-ball helper.

Smart executed the game plan to perfection, shadowing Korver by angling his body to go through and around screens with power and finesse.

The Hawks didn't even make a full effort to get their weapon going against Smart. They used him as a decoy, like an NFL team would use a receiver against a shutdown corner. Atlanta knew any attempts would be futile.

But a change to the defense was necessary because Paul Millsap was doing his best Mike Tyson impression by knocking out everyone in sight. The Atlanta forward had 41 points midway through the fourth quarter when Stevens gave his 6-4, 220-pound guard a new assignment: contain the 6-8, 246-pound three-time All-Star. "Coach was like, 'You know what, we got to try something new.' And he looked, turned at me, and said, ‘Marcus, guard him.' And that's all he said," Smart explained. "I just kind of looked like, ‘OK.'"

Watch the video above for all of Smart's possessions against Millsap.

Millsap shot just 1 for 5 while being defended by Smart. Millsap has a size advantage, but the Celtics guard is one of the NBA's strongest pound-for-pound players. Smart outmuscled Millsap off his spot on the post and boxed him out of rebound positioning.

"We obviously were running out of bodies because everybody had gotten a crack at him and he had 45, so I think it's a combination of things," Stevens said when asked about the decision to try Smart on Millsap. "Marcus is an excellent defender with great strength, so he's able to make post catches difficult, he's able to guard him on the drive, maybe not as much in the deep post, but he didn't let him catch it in the deep post. And then he did a great job getting him off the glass."

Smart is one of the few players in the NBA capable of defending all five positions on the floor, which is why he's able to contain two drastically different players in Korver and Millsap. He also defended Thabo Sefolosha, Kent Bazemore, Dennis Schroder, and Jeff Teague. Combined, the Hawks missed 10 of 12 shots and had two turnovers while being defended by Smart. That level of elite versatility is what makes him so unique, and Smart likes the sound of not having a label placed on him.

"I'm a basketball player. I don't really define myself as any position. I think that's what's been so unique about me growing up and playing ball," Smart said. "It's kind of hard to define my position, and it's kind of hard to see who you're going to put on me because of my versatility. As crazy as it sounds, yes, I've guarded a 7-footer [Knicks rookie Kristaps Porzingis] and things like that. And going to guard other bigs, and then covering the guards, it's tough. But I pride myself on defense. This team knows that. My teammates know that. And the coaches know that. And they trust me to do that."

Trust isn't a word you hear associated with Smart very often, even though you should. The coaches certainly do have it in Smart. Stevens added: "I thought Marcus just played a great game, period. And we've talked about it before. Like, Marcus has had his ups and downs. But Marcus, on this stage, with his consistent work ethic, and with his competitive spirit, you really trust that good things will happen. And so we trust in him and he did a great job tonight on both ends on anybody he was assigned to."

The disparagers talk about Smart's flopping, reckless shots, shooting struggles, and forced plays. So the positives get disregarded: his progress as a passer, scoring flashes, clutch shooting, rebounding, and defense. But no player is flawless, never mind a 22-year-old second year pro. The team understands that.

"His aggression, his competitiveness, his spirit, like, our team needs it," Stevens said. "There's going to be some times where he might take a shot or whatever the case may be that he'd like to have back, but he does a lot of good things that lead to winning and give you a chance to win. And defensive versatility's at the top of that list."

"He's unbelievable," Evan Turner said after the game. "When he starts scoring offensively and he gets his playmaking down, he'll be an exciting player to watch. I thought tonight he was the best player on the court."

Transcendent is defined as "extending beyond the limits of ordinary experience." It's safe to say Marcus Smart's master class of a defensive performance in Sunday's win was as transcendent as it can get. It won't be long before it's a ho-hum statement to call Smart "the best player on the court."

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