BOSTON — Marcus Smart is many things, including the father of every “Marcus Smart Play”—thrilling, borderline-spiritual events that can be self-destructive and immeasurably beneficial at the exact same time. They’re incendiary sequences, spontaneous displays of physical brilliance that swerve off road without warning.

Whether he skins his elbows during a kamikaze slide for a loose ball or draws the type of charge that his 45-year-old lower back will never forgive, Smart's addiction to sacrifice is admirable and unmatched. Sometimes he plays with too much intensity, if such a thing is even possible.

“It’s hard to say in words what Marcus does,” Danny Ainge told VICE Sports after the Boston Celtics went up 2-0 in the Eastern Conference Finals. “The fire that’s in him to win, and win at all costs, is contagious.”

The standout "Marcus Smart Play" from this postseason came at the climax of the most recent playoff series Boston was not expected to win. Up one with two seconds left in Game 5 of the Eastern Conference Semifinals, Smart missed his first free-throw and then made his second after he purposely tried to miss it. A few seconds later he intercepted Ben Simmons’s full-court Hail Mary heave, traveled (it wasn’t called), and flung the ball 30 feet in the air as time expired.

That sequence so accurately defines the Marcus Smart experience that it was a bit too on the nose. The 24-year-old is also known for a different kind of play that embodies how abruptly he can single-handedly alter the feel and trajectory of an entire matchup. More often than not, these are unfathomably spectacular feats on the defensive end that ooze a certain amount of versatility, athleticism, and basketball bravery that’s unheard of from someone his size.

A dozen examples from this postseason alone come to mind, but the one that stands out for multiple reasons happened during Boston’s first round match-up against the Milwaukee Bucks. In the middle of March, Smart had surgery on his right thumb after he injured it tracking down a loose ball, making the play seen below his first taste of live basketball in six weeks. It just so happened to be in Game 5 of a tied series, which is typical Marcus Smart.

It’s a side pick-and-roll run designed to clear one side of the floor so Giannis Antetokounmpo can set a screen and then dive to the rim. The Bucks try and switch Smart onto Giannis at the start, but he quickly fights off it and scurries halfway back to Tony Snell. Most defenders (and just about every guard) would drift toward the weak-side corner and cover their own man. Smart is not most defenders. Not only does he sniff out exactly what Matthew Dellavedova wants to do before he does it, but he then meets Antetokounmpo about a foot above the rim with his left, non-surgically repaired hand to break up a sure two points.

Only so many players have the brain and body to pull something like this off, and a large percentage of that same population would never willingly subject themselves to humiliation like Smart does. Even though the moment doesn't allow any time for him to shake off rust, show hesitation, or behave like a normal human probably would, Smart doesn't think that way. He brings a unique dauntlessness to the table at all times, and annually dials up his own ferocity to a dangerous level in the playoffs.

“The fire that’s in him to win, and win at all costs, is contagious.”

Despite his porous three-point percentage (he made 28.3 percent of his wide-open threes this season, a number that's barely cleared 20 percent in the playoffs) and inability to finish around the rim, plays like the one seen above help explain why Smart is one of 18 players over the last three postseasons to log at least 1000 minutes. (Ten are or were Golden State Warriors or Cleveland Cavaliers.)

This environment is when Smart’s unparalleled tenacity shines. During Tuesday night’s Game 2, he deflected four passes, recovered four loose balls, and contested more shots than anyone in the game except Tristan Thompson (a center who played as many minutes). Boston outscored Cleveland by 21 points when he was on the court.

“If it’s a 50-50 ball he’s gonna get it. If it’s a loose ball, offensive rebound they need to have, he’s gonna get it,” Cavaliers head coach Ty Lue said. “So we’ve gotta be able to find someone who can match his toughness.”

A few minutes after Lue gave that answer, LeBron James stepped to the podium and I asked him about Smart’s impact on the series. “I think Marcus always makes plays at the right time...He’s always been very productive for their ballclub,” he said.

Boston’s defensive rating in the playoffs is a team-low 98.9 with Smart on the floor. It rises to 108.4 when he isn’t in the game. The gap between those two numbers is “best defense in the postseason by a few points” and “the Cleveland Cavaliers.” Smart’s combination of strength, speed, and intelligence is almost unheard of on that end. The ability to handle J.J. Redick in one series and then capably switch onto Kevin Love in the next is as impressive as it is rare.

And as seen on that highlighted play against the Bucks, Smart is a critical help defender. He stunts at the right time, calls out switches, and directs traffic as the Celtics race back to guard the other end. (According to Cleaning the Glass, Boston’s defense in transition has been terrific with Smart on the court in three of his four seasons after its opponent grabs a defensive rebound.)

“I’ve been a great defender my whole life,” Smart tells VICE Sports. “It’s kind of embarrassing when I see or hear people and I’m not even mentioned in any defensive teams or discussions or anything like that. It’s a slap across the face. I get it. It’s about popularity. You tell me who in the league is a better defender than I am, especially on the perimeter. There’s not many guys. Guys in this league know the type of defender I am, and they know when you go up against me you’ve gotta bring it because I’m gonna bring mine.”

Photo by Greg M. Cooper - USA TODAY Sports

“Marcus Smart Plays” can be breathtaking, but they also tend to degrade the total picture. Smart is so much more than an intelligent energy supplement with All-Defensive-team-caliber attributes. Put the ball in his hands and he transforms into a maestro. “He’s a really good ball-handler, he’s a good playmaker, he’s a great passer,” Brad Stevens says.

It's this realm where some of Smart’s most important contributions get clouded by his impotent individual shot creation. Liquid hustle flows through his veins, but Smart is also one of Boston’s most reliable play creators. Despite missing the team's first four playoff games, he’s still held the ball for more minutes than everyone on the team except Terry Rozier. Only Rozier and Shane Larkin average more seconds and dribbles per touch, and Smart leads the team in assist rate. (He was second only to Kyrie Irving during the regular season in that last category, at a number that’s about 10 points higher than it was two years ago.)

The aforementioned drawbacks pop up all over the place, too. Smart is literally the least efficient pick-and-roll scorer in the entire postseason, somehow shooting 19.2 percent on 26 shots with the lowest points per possession average among all players who’ve logged at least 10 possessions. But those weaknesses never engulf other areas where he’s as productive as they come. According to Synergy Sports, Boston’s averaging 1.45 points per possession whenever Smart feeds a roll man, cutter, or spot-up shooter when dribbling off a screen—good enough to land him in the 96th percentile.

Pick-and-roll manipulation is one of Smart’s subtlest strengths. He’s mastered how to control timing, get low enough to turn the corner, and catch defenders off balance with shoulder fakes, hesitation dribbles, and one-handed, off-the-bounce lobs tossed a beat early. Against switch-happy defenses (like Cleveland and whichever team Boston may face in the Finals) Boston’s screeners release as quickly as they can to create a target Smart can hit with ease.

“We try to get out of screens quick and try to find a seam to the rim either on the drive or a lob,” Stevens said when asked about this play after Game 2. (PSA to Lue: Putting Kevin Love on Smart probably won’t work going forward.) He's also so good at moving back-line defenders with his eyes and whipping pocket passes high enough off the floor that someone like Aron Baynes doesn't have to bend over to retrieve it.

Some of Smart's success is thanks to a partnership with Horford, a three-point threat who can pop or roll with the best of them. Smart also has the privilege of conducting an offense that can space the floor and knock down open shots. With Gordon Hayward and Irving injured, and Jayson Tatum and Jaylen Brown not quite ready to set the table, he heightens a role the team won't need him to fill forever. And at the end of the day, with restricted free agency just over the horizon, the Celtics need to ask themselves how important everything Smart brings to the table actually is.

Right before the trade deadline, during an 11-game stretch in which Smart was sidelined after he punched a glass picture frame and lacerated his hand—a move that almost led to season-ending surgery—I inquired about Smart’s trade value and looming monetary worth with a few people around the league. The feedback was like a prequel to Yanny vs. Laurel.

Descriptors like “polarizing” and “weirdly divisive” never strayed far from those conversations, as reports that Boston was actively shopping him grew louder and louder. According to Ainge, the Celtics never went deep into negotiations on a trade involving Smart, though. That's partly thanks to inadequate offers and the understandable disconnect between how Boston views his impact and the glaring flaws seen by the rest of the league. Smart's effective field goal percentage has never sniffed league average and in a situation where someone else is running the show, he can’t space the floor. (It’s not a definitive statement either way, but Irving had more individual success without Smart than beside him this season.)

“People talk about him all the time. Sometimes they focus on things that don’t matter,” Stevens says. “And other times they focus on that he impacts winning. We’re really glad he’s on our team.”

Ainge echoed the sentiment: “I don’t know how people [around the NBA] value players.” he told VICE Sports. “I only know how much I do. I love having him on my team and I love the fact that his teammates enjoy playing with him.”

And still, once this playoff run ends, the Celtics will have to figure out how much they want to pay one of the NBA’s least efficient players. It’s precarious and complicated for a variety of reasons, and as the organization’s longest-tenured player (literally no one from Stevens’s first season is still around), how do they assess a player who provides an unquantifiable advantage while simultaneously existing with weaknesses that really stand out? Right now, not even Ainge has an idea of how everything will go. “I don’t know. It’ll be interesting,” he says.

One coach in the Western Conference recently told me he sees Smart as an “identity piece,” meaning that over everyone else on their roster, Smart is the fabric the Celtics most aspire to use in stitching what they want to be together. He’s essential to what they are, and his best days lie ahead.

"I love having him on my team and I love the fact that his teammates enjoy playing with him.”

That point is debatable, and an open marketplace, crowded Celtics roster, and legitimate long-term luxury tax concerns are more relevant to this discussion, particularly when weighing how much money another team may offer to pry Smart from Stevens’s system (and Boston’s culture). As a restricted free agent, there aren’t many clubs with space and a dying need to overpay for Smart’s skill-set. He isn't a building block or starting point guard. Fit always matters.

Should no attractive offers trickle in, it'll be up to Boston to commit enough to dissuade Smart and his agent from playing next season on his qualifying offer and then re-entering the marketplace as an unrestricted free agent the following summer, when a lot more money and several more destinations shake free. In the meantime, would he accept something like $40 million over four years? The Celtics would be under the tax by about $4 million with that agreement—assuming they sign their 2018 first-round pick—but Baynes and Larkin aren't included.

Even though there's value in locking Smart up on a tradable contract, his role on next year's team (and beyond) could rapidly diminish if Rozier sticks around. And with Irving and Hayward healthy, would Smart even be on the floor at the end of a playoff game next year, taking minutes away from those two All-Stars, Brown, Tatum, and Horford?

Smart is important, awe-inspiring, and somewhat of a religious experience. He's adaptable to just about any style of play and makes his presence felt in ways sixth men typically can't. But he’s also a puzzle piece. The Celtics know this, and aren’t afraid to part ways with even their most beloved contributors.

“Marcus is a really good player. Every player, they contribute in different ways. We couldn’t have done this season if we didn’t have lot of guys out there, and they’re all tough to replace. It’s tough to replace Kyrie and Gordon. I think all the time, like, ‘Man, we’d be even better with them.’ It’s just so frustrating, but at the same time it’s been fun really watching this team,” Ainge says. “But I think the beauty of this team is that there’s been so many guys. Marcus has missed a lot of games this year and we won a lot of those games. And so we find ways. I’d say Marcus brings something that others don’t bring. I mean, everybody brings something different to the table.”