It wasn't the Christmas gift Marcus Smart asked for.

Midway through the second quarter of Boston's holiday visit to play the New York Knicks, Smart looked up to find 7-foot-3 big man Kristaps Porzingis sprinting down the lane at him. Considering Porzingis' penchant for poster dunks early in his NBA career, Smart could have been forgiven if he elected to simply step out of the way. But that's not in Smart's basketball DNA, so instead he cemented his feet in front of the charge circle and braced for the inevitable collision.

Porzingis tried to dump the ball off at the last second, but still plowed hard into Smart, who toppled backward and earned the charge call for his trouble.

Smart ranks among the NBA's leaders in charges drawn this season, having absorbed 18, according to the league's player-tracking data. That ranks sixth overall, but that's a lofty position for a guard in a category that's dominated by big men who rack up charges as the last line of defense.

Smart accounts for one-third of Boston's total charges drawn this season. In fact, Smart ranks third in the league in total offensive fouls drawn at 42, trailing only Houston's Patrick Beverley and Atlanta's Ersan Ilyasova, according to stat-tracking website NBA Miner.

All the grumbles about Smart's propensity to flop tends to mask the fact that he is far more likely to sacrifice his body for the betterment of his team than embellish contact. And Smart, who has been much better lately at limiting those flops, takes great pride in the fact that he has emerged as one of the best charge-takers in the NBA.

"It just shows that I care more about my team than myself and that I’m willing to give up my body," said Smart. "It takes somebody real selfless to take a charge. You got to be real unselfish to take a charge, because you know you could possibly get hurt. You know you’re going to get hit. But you’re not thinking about that. You’re thinking that this is something that’s going to help my teammates and my team."

The Celtics' Marcus Smart takes a charge against the Cavs' Derrick Williams last week. Smart is among the league leaders in drawing charging fouls with 18 this season. Greg M. Cooper/USA TODAY Sports

So what exactly makes Smart so good at drawing contact from offensive players?

"I think he’s got two things: One, he’s not afraid to put his body on the line," said Celtics coach Brad Stevens. "No. 2 is he’s got great instincts to beat people to a spot. I think he does a good job of knowing people’s tendencies, knowing what they want to do, the directions they want to go.

"But then he plays with multiple efforts to get there. And then, you know, it’s easier said than done to be willing to step in front of some of these guys driving the ball. He does that over and over."

Just check out the final three minutes of Wednesday's thrilling victory over the Cleveland Cavaliers for confirmation. Smart absorbed a pair of charges 31 seconds apart to give Boston a chance to rally. On the first, Smart was scrambling out to contest a Derrick Williams' 3-pointer but as soon as he saw Williams put the ball on the ground, Smart alertly shuffled to a spot where he was able to eat a shoulder and draw the whistle. Soon after, Smart watched a cutting Williams take a pass in the paint and somehow teleported himself to a spot just outside the charge circle where he again got crunched by Williams but earned another whistle.

Twice, the Cavaliers could have made it a two-possession game. Twice, Smart came up with the sort of momentum-changing play that gave Boston a chance to steal a win.

Smart has plenty of bruises to show for his efforts but is adamant that none of the charge takes were painful enough to regret them.

"Nope, never [any regrets]," Smart said. "My high school coach always told me that a charge is the best play in basketball. First off, nine times out of 10, it’s going to be a personal foul on one of the [opposing] team’s most valuable players. Two, it’s a turnover. Three, it’s a big momentum boost for your team. Four, you get the ball back."

Smart is averaging career bests at 10.6 points and 4.5 assists in 31 minutes per game. His shooting has steadily improved this season -- although he shot down this reporter's playful suggestion that Smart's recent haircuts might have contributed to his improvements. It's been his ability to calmly run the second-unit offense -- filling the void left by Evan Turner's departure -- that has made him especially valuable for Boston.

Well, that and Smart's unrelenting defense. Opponents are shooting just 41.4 percent when Smart is the nearest defender, according to the league's player-tracking data. That's 3.4 percent below those players' season averages.

Not surprisingly, Smart's name is all over the NBA's hustle stats database. Beyond the charge takes, he also leads the Celtics in deflections (178) and contested 3-point shots (205). He's second on the team in loose balls recovered (56) and has slowly been creeping up behind Isaiah Thomas (59).

But not even the league's variety of hustle stats can quite quantify the impact that Smart has on winning. Yes, Boston's on/off splits speak to his influence, as the Celtics own a net rating of plus-4 points per 100 possessions when Thomas is on the floor and the team's defensive rating spikes by 4 points when Smart is off the court.

Still, there's no metric that can accurately measure all the rebounds that Smart keeps alive by sheer determination or how much his willingness to guard bigger players -- such as all those turns he's taken on Porzingis the past two seasons -- helps an undersized Boston team.

Smart, the No. 6 pick in the 2014 draft, will celebrate his 23rd birthday on Monday. He's still developing, particularly on the offensive end, but the Celtics are putting him in position to thrive.

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Stevens loves sending Smart to the post and letting him take advantage of undersized or weaker guards. On a team thin on bigs willing to consistently post up. Smart trails only Al Horford in post plays finished this season. Smart averages 1.07 points per play in those situations, ranking him in the 90th percentile among all NBA players, according to Synergy Sports data.

Drill down to players with at least 70 post-ups finished, and Smart ranks fourth in the NBA, sitting behind only Denver's Danilo Gallinari (1.163), Toronto's DeMar DeRozan (1.145), and San Antonio's Kawhi Leonard (1.116).

While Smart ranks in the 16th percentile while averaging just 0.813 points per play overall, his value is emphasized when you look at Synergy's plays-plus-assists metric. His production spikes to 1.246 points per play in that instance, elevating him to the 74th percentile.

Smart might not be a starter, but he plays big minutes for a Boston team with plenty of guard talent. He's a big reason the Celtics are second in the Eastern Conference. And while the stats don't always make that obvious, it's the little things like charges that hammer home his impact.