DENVER — When Marcus Smart was drafted sixth overall in 2014, he was slated as the Celtics’ point guard of the future. He was a combo guard at Oklahoma State, but because of his lack of perimeter shooting skills and his size, he was projected to play point in the NBA.

Smart’s first 1½ seasons in Boston haven’t quite worked out that way. Instead of point guard, Smart plays agitator, spark plug, stopper, antagonist, and bruiser. The Celtics entered Sunday’s contest against the Nuggets having been battered Friday in Salt Lake City, allowing 111 points as the Jazz sliced through the Boston defense.

Realizing their defense had been slipping the past five games, the Celtics put more emphasis on the dirty work Sunday, and there is no Celtic more representative of that category than Smart, who scored 10 points with four steals as he guarded nearly every position in a 121-101 bounce-back win at Pepsi Center.

What has become evident about Smart is he doesn’t have a true position, which has become a strength in today’s NBA that emphasizes versatility, especially on defense.

The reason Michigan State’s Draymond Green dropped to the second round of the 2012 NBA Draft was that he really didn’t have a set position. He played all three frontcourt spots in college, but at 6 feet 7 inches, scouts believed that wouldn’t be possible in the NBA.

The same could be said about the 6-4 Smart, who hounded nearly every Nugget on the court with his trademark toughness.

Smart is indeed a bull in a china shop. The Celtics have been horrible at fouling this season, quickly putting opponents in the bonus with overaggression.

Smart has had the most trouble with that, but it’s truly something he can’t help. He plays with a relentless style. He likes the physicality, and officials have penalized that style with fouls.

Smart averages three fouls in 27 minutes per game this season, and picked up five in 32 minutes Sunday, plus a technical foul when he screamed for a foul after a layup; he claimed he was signaling “good pass’’ to a teammate.

Celtics coach Brad Stevens understands that Smart is going to make aggressive mistakes at crucial moments. There was the late foul at Memphis last month against Mario Chalmers that sent the Grizzlies guard to the line for two critical free throws when the Celtics needed a stop.

Smart doesn’t know the meaning of “lighten up’’ or “take it easy,’’ and that is what makes him such an abrasive defender.

“You coach each guy a little bit differently,’’ Stevens said. “But I think the spirit and competitiveness are things you prioritize above all else when you’re coaching him. You don’t want to hinder that or hamper that.’’

So Smart isn’t the Celtics’ point guard of the future or even perhaps their shooting guard of the future, but he is a versatile defender with offensive potential, a player every team would like to have.

After Thursday’s practice, Smart got into a friendly but competitive exchange with Isaiah Thomas about whether he stripped Thomas clean without fouling.

Thomas thought he was fouled. Smart, of course, thought it was a clean play.

Smart can’t change his style, but he realizes he needs to make adjustments. He has to be better aware of the officiating, especially in situations where the Celtics are near the penalty. He has to make intelligent fouls and stay away from reach-ins 40 feet from the basket.

But he is one of the reasons the Celtics are a sparkling defensive team, because of his ability to guard three positions. And then there are plays such as Sunday, when Smart slapped a loose ball down the floor. Evan Turner raced to retrieve it and then flipped the ball to Avery Bradley for an uncontested dunk. Denver’s players didn’t even move.

Smart is a master of making plays that don’t necessarily show up on the stat sheet, which has made him invaluable.

“You’ve got to keep that aggressiveness,’’ he said. “But at the same time you’ve got to realize how the refs are calling them. But you don’t want to take away from you being you. I might have to take a little bit off but definitely keep the pressure on. Don’t stop being you.’’

Harnessing his aggression and getting more respect from officials will come with experience. Smart’s playing time has been cut short because of injuries as he has no issue sacrificing his body, such as late in the third quarter Sunday when he took a charge from 280-pound Jusuf Nurkic under the basket. Smart arose quickly after the contact and sprinted down the court, his defense gaining another possession for his team.

There are going to be moments when Smart doesn’t always make the more intelligent play, but those are far overshadowed by those hustle plays and fearless plays that help seal wins.

Now all Smart needs is a little respect from the officials.

“I figure being in my second year, they’ve seen me enough, they know I’m an aggressive player,’’ he said. “They know I’m a defender, so I feel like some of those calls, especially when both guys are battling, just have to let us play.’’

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.