BOSTON -- Marcus Smart's phone was buzzing as he looked down: "Mama." He had a good idea why she was calling.

It was late, but his 63-year-old mother, Camellia, has been staying up back in Texas to watch his game, even as she battles a recent cancer diagnosis.

"She calls me and she yells at me. She tells me to calm my 'so-and-so' down," Smart said.

Earlier that night, Smart had angrily stomped in the direction of Philadelphia 76ers rookie Ben Simmons after a flare-up between the two in the final moments of Boston's Game 1 triumph.

"She tells me breathe and keep going and know that's what people are going to try to do, get in my head, and force me to do those type of things, Smart said.

"Just keep my cool."

Smart smiles as he recounts what has become familiar advice from his mother, because he now sees the bigger picture: It's good to be playing basketball; it's good to be talking to Mama.

The past three months have put it all into perspective for Smart. He missed the final 11 games before the All-Star break after punching a glass picture frame out of frustration in a hotel room in Los Angeles. Doctors told him to play the lottery because he came inches away from shredding a tendon that could have ended his season.

Eight games after his return, Smart tore a ligament in the same hand while diving for a loose ball and missed the final 15 games of the regular season.

"I've never had a coach from another team say anything but, 'That dude's a total winner.' Ever."

There was no guarantee that the injury-ravaged Celtics would still be playing by the time Smart was healthy enough to return to action after surgery. And during Smart's rehab, Camellia revealed she was diagnosed with myelodysplastic syndrome, a bone marrow cancer, and Smart flew home to Texas to be with her amid an uncertain future.

Camellia implored Smart to return to Boston. She promised the sight of him back on the basketball court would be her best medicine -- his occasional on-court dustups notwithstanding.

Smart heeded his mother's advice and rejoined the team, and the Celtics probably don't win Game 5 against the Milwaukee Bucks -- or maybe the series -- without his efforts.

Boston has won three of its four games since Smart's return and own a 1-0 series lead over the Sixers entering Thursday's Game 2 of an Eastern Conference semifinal series at TD Garden.

Celtics big man Al Horford calls Smart the "soul" of the Celtics and he might also be the poster child. Battered and bruised, Smart is out here helping the Celtics win games on little more than hustle and grit, and even those little on-court flare-ups that distinguish Smart from everybody else.

He wants to win so badly that his temper sometimes gets the better of him. But that drive is the same reason why he wins most scraps for a loose ball.