Statistics are a great part of the basketball. They can tell you all kinds of stories. With traditional stats, we can see who scores a lot of points, gets boards and shoots at a high percentage. With advanced numbers, we can tell tell how much of a defensive impact five-man units have and how well teams are converting in different sets.

All of this is important information, and we lean on a combination of traditional and advanced stats to tell us who is good and who isn’t as a result. Good players have good stats; it is usually that simple. But sometimes statisticians find an anomaly who’s hard to define—a player who goes against conventional wisdom with their impact.

A player like Marcus Smart.

Smart is not a prolific offensive player; he averages a mere 9.5 points per game. He is not a great shooter (29.1 percent overall and 28.0 percent on threes), nor does he impress with the number of rebounds he is pulling in (4.3 per game). The only impressive offensive figures for Smart are his assist numbers (5.5 per game), which are only enthralling because he is playing off the bench. Even his defensive numbers don’t blow you away. He is 16th in the league in steals (1.6 per game). According to NBA Math’s defensive points saved metric, Smart ranks 25th in the league (17.37).

Despite all this, he is continually in crunch-time lineups for the Boston Celtics, the team with the NBA’s best record. Why? Because he does things on the court that former teammate Jae Crowder once called “winning plays.”

“A guy like him is hard to keep off the court because he makes those winning plays—a dive on the floor, getting a steal, rebounds. He makes those types of plays and that’s why we need him on the court,” Crowder told ESPN’s Chris Forsberg. Night in and night out, Smart makes plays in which the impact on the game is hard to quantify.

When I played high school basketball, I had a coach who called this “doing the little things”. Undertakings like boxing out, taking charges, making good entry passes and contesting without fouling are essential to winning teams but don’t all show up on the stat sheet. Smart excels at doing these dirty deeds, hence why he’s a key part of so many crunch-time units for Celtics head coach Brad Stevens. Let’s take a look at his complete oeuvre to get a better sense of what makes him such a valuable player.

Imposing His Will Defensively

The Celtics are a high-IQ team that uses defensive schemes to create advantageous situations, kind of like a spider web trapping opponents into bad attempts late in the shot clock. When the defense is functioning at peak efficiency, every move is carefully laid out for the unsuspecting offense to work itself deeper into the web—a shot by a bad shooter here, a pass into traffic there. In the middle of this web is the spider, Marcus Smart, Boston’s best perimeter defender, executing the stranglehold that leads to turnovers.

Watch him here as he causes Russell Westbrook to travel. Marcus Morris and Al Horford have doubled Steven Adams to stop the entry, Kyrie Irving is preventing the skip to the corner and Smart stays in front of Westbrook, who’s out of options:

Smart has a veritable repertoire of ways to deal with these situations, ranging from simple, like playing off 29 percent three-point shooter Andre Roberson to entice a bad attempt with a full nine seconds left on the shot clock:

To this complex defensive series where he switches onto Shelvin Mack, traps the baseline and hedges on penetration before finally closing toward the corner to prevent a three-pointer:

Smart does nothing that registers on the stat sheet in either situation. And yet, he’s the reason these gambits are successful. The Celtics are consistent beneficiaries of these carefully cultivated schemes in which he functions as the linchpin of the league’s best defense.

Boxing Out

In the modern world of pace and space, rebounders usually establish good position, high point the ball and get a board—a fine strategy if you are the biggest or most athletic player on the court. At 6’4″, Smart must take a different tactic on the defensive glass. By using his stocky frame, he can prevent opposing big men from rim-running for offensive rebounds. Watch on this play as he boxes out Steven Adams to neutralize a put-back. Adams has a great angle on the basket, but Smart’s box-out allows the ball to fall into empty space before it’s picked up by Aron Baynes:

This tactic has changed things for the Celtics. Their defense was maligned for two major reasons just a season ago: They were a poor defensive rebounding team (22nd in the league), and they allowed too many second-chance buckets (27th). Smart has been a major contributor in limiting these weaknesses for the new-look Celtics, who rank third in rebounding and fourth in second-chance points allowed.

The real key to success on these plays? He oftentimes doesn’t even get the rebound. Look below as he boxes out Andrew Bogut, preventing him from crashing the offensive glass, while Terry Rozier secures the board:

Smart’s rebounding numbers are deceptive; he is doing the lion’s share of the work on this play, but someone else gets a tally on the stat sheet. The impact he has on plays like these is hard to calculate with numbers, but the more you watch him, the more you see things like this happening on every single trip down the floor. He is making a big impact on stopping defensive possessions, even when the stats don’t show that outright.

Contesting Without Fouling

Smart can also be a tenacious rim-protector, often challenging a driver’s path to the rim or flat-out blocking shots. He has an incredibly strong lower body, possesses nimble feet and is a quick leaper, which allows him to establish position between a slasher and the hoop and jump straight up to alter a shot without initiating contact. On the below play, he is backpedaling in transition, sets his feet and challenges the 6’9″ Julius Randle at the rim. The power forward misses, and the Celtics get the ball back on a Daniel Theis defensive rebound:

The value of this cannot be overlooked. Fast breaks are usually high-percentage opportunities (the Lakers convert on 49.3 percent of their transition looks), but disrupting one and grabbing a defensive rebound is almost always an appreciable two-point bid…and sometimes a four- or five-point swing.

Smart is also a deceptively good shot-blocker. On this play, he meets Lonzo Ball at the rim and rejects a layup attempt after coming from the weak side as the help defender:

Smart isn’t known for his shot-blocking ability, even among guards. But his capacity to make these plays is why the Celtics use him as a defensive crutch in exigent circumstances. And that’s not all. He has another tool he breaks out to end possessions.

Defense to Offense

Smart is, to borrow a football term, an active free safety who gets into passing lanes and creates steals of his own. But his vision is what makes these plays so valuable. In this clip, he steals the ball from Evan Fournier, identifies the three-on-two and pushes it ahead to Semi Ojeleye for the basket:

As discussed above, this play results in a four-point swing. And, really, it’s more than that—an added possession that would not have existed without Smart. With only 12 seconds left in the half when Fournier got the pass, the Celtics weren’t going to get the ball back. But Smart’s quick hands and court vision generated another scoring chance.

And he doesn’t even have to initiate the steals to get these plays started. Marcus Morris forces a change of possession in the below clip, and Smart still looks to run in transition:

As soon as Jayson Tatum sees the ball is loose, he leaks out, and Smart finds him for the easy bucket with a nice outlet pass. These fast-break chances off turnovers are huge for an offense that plays at one of the league’s slowest paces.

Second-Chance Opportunities

Smart generates extra possessions on the offensive end, as well. He is not afraid to go in among the trees and chase rebounds when his team needs one. Watch how Smart outworks Raymond Felton, Paul George and Alex Abrines to get a pivotal rebound, then draws a foul:

In close games, second-chance plays go well beyond a rebound and two free throws. Hustle like that is likely to spark runs or inspire teammates, and Smart excels in this area. He spearheaded two pivotal runs in the above game alone—one closing the lead from 18 to four at the end of the third quarter, and another 22-15 spurt to end the game.

Dirty-Work Extraordinaire

Smart will do just about anything to help his team win—whether defending, rebounding, protecting the rim or just getting on the floor to recover a loose ball:

He is ready to bring his lunch pail and go to work. Every. Single. Night. Every team in the league would love to have a guy like him, even if his shooting numbers can trigger bleeding in the eyes.

This summer will be interesting for that exact reason. Smart and the Celtics couldn’t agree on a contract extension before the season started, so he will be a restricted free agent. Suitors will likely come knocking with large offer sheets to try luring him away, particularly with Boston’s precarious salary cap situation. Most competitors would likely love to have his hard-nosed mentality on their rosters.

After all, everyone wants a player who makes “winning plays”.

Follow Alex on Twitter @AlexWestNBA.

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Unless otherwise indicated, all stats are from NBA Math, Basketball Reference or NBA.com and are accurate heading into games on November 12.