BOSTON — Marcus Smart doesn’t care about the effect the hardwood can have on human flesh. He plays with the abandon of a hair-on-fire stuntman for his Boston Celtics, diving then crashing to the floor while pursuing a loose ball.

His bandaged right wrist should serve as a reminder of recent surgery, but that does not seem to cross Smart’s mind when he belly-flops onto the leather shoes of the Cleveland Cavaliers’ coaches.

On Tuesday night – as the Celtics took control of the Eastern Conference finals, defeating the Cavaliers 107-94 for a 2-0 series lead – Smart created one of his signature moments.

During the fourth quarter, Smart poked the ball away from Cavaliers forward Jeff Green then launched himself to the sideline to save the possession. The Cleveland bench complained Smart was out of bounds, but the play went on. After creating an uprising among his rivals, Smart simply returned to his feet and rushed back into the breakneck action.

Smart performed as a tone-setter, finishing with an all-around line of 11 points, nine assists, five rebounds and four steals.

“He’s always going to play hard,” Celtics guard Terry Rozier said.

“That’s what Smart does, man. Smart was born with his hands dirty,” forward Jaylen Brown praised.

“He does anything that the team needs to win,” backup big man Greg Monroe said.

The interpretation of “anything” also means mixing it up when necessary. Later in the fourth quarter, Al Horford thought he had a breakaway layup but Cavaliers guard JR Smith shoved him with two hands, sending Horford to the floor.

Smart remembered the first-round playoff series against the Cavaliers three years ago when Smith elbowed former teammate Jae Crowder. And this year, the Celtics hadn’t had the best of luck with guys falling after midair collisions – for instance, Gordon Hayward, lost for the season in the year’s first six minutes of action. Smart, who later described Smith’s actions against Horford as “dirty,” reacted impulsively, shoving Smith, who shoved back. Both drew technical fouls.

“They’re helpless,” Smart said of players driving to the rim. “They can’t protect themselves. We’re out there to play basketball. We’re not out there trying to hurt anybody. That’s just a play that you just don’t do.”

‘OUR LAST HOPE’

This instinct to protect has been in Smart’s DNA since childhood. The youngest of four boys, Smart lost his oldest brother, Todd Westbrook, to leukemia when he was 9. He can still hear the voices telling him to wipe away his tears, toughen up and step up in the family.

“‘You our last hope that we got for this family,’ and I took that hard in consideration,” Smart said. “Every night I’d just go to sleep and cry myself to sleep because I knew the pain my mom and family was going through. Some nights not being to be able to eat. Some nights not knowing (what) we were going to do and I just promised my mom, I’m going to make it for us.”

Initially, this mandate was too much for a child. Smart wanted to be like anybody else his age, free of responsibility and burden.

“At the time, I just wanted to be a kid. I’m thinking about going outside, playing video games, playing with my friends. You know, I didn’t have that luxury. I never had a spring break. I’ve always been on the road. I’ve always been traveling,” Smart said. “I’ve always been playing because I knew this was eventually going to pay off.”

Now, it’s paying dividends for the Celtics and brewing envy within the Cavaliers.

After the game, Cleveland Coach Tyronn Lue joined the chorus.

“He makes winning plays, he makes tough plays,” Lue said. “Like we said before, if it’s 50/50 balls, he’s going to get it. If it’s a loose ball, offensive rebound they need to have, he’s going to get it. We’ve got to be able to find someone who can match his toughness.”

AN UNSELFISH PLAYER

From their seats inside the TD Garden Arena, Ted and Kimberly Williams did not marvel.

They’ve seen this act before. Many years ago inside a Flower Mound, Texas, high school gymnasium, they watched the kid collect floor burns like loose change and play an unselfish brand that converted a football-crazed community into Smart disciples.

“I don’t know where it came from but that sucker is tough,” said Ted Williams, whose sister was the principal of Edward S. Marcus High in Flower Mound, when Smart was in school. “If you watch (number) 36 play and you can’t love that style of basketball, you’re not a basketball fan.”

Although the Williamses reside in Leonard, Texas, the couple became fans and made weekly 60-mile trips to watch Smart play.

“The first game I went to, he turned down a breakaway slam dunk to pass it back to Phil Forte … to shoot a 3-pointer,” said Williams, who displays 500 of his Marcus Smart rookie cards on his pool table back home.

“And I was hooked at that point.”

Smart smiles at the memory of that play – sharing the ball with his best friend who would later attend Oklahoma State with him. The unselfishness remains as one of Smart’s best qualities – especially when he sacrifices himself on the sideline.

“He didn’t quit. You saw it – I mean, gah!” said Kimberly Williams, a chuckle catching in her thick southern drawl as she recalled Smart’s diving save.

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