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.
"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."Celtics coach Brad Stevens, on Marcus Smart
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.
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.
"I think it all starts with his competitiveness," Celtics coach Brad Stevens said. "He has the ability to make plays that nobody else makes. Like, whether it's ripping the ball out of somebody's hands, or the [offensive rebound] he made against [Sixers 7-footer Joel] Embiid where he laid it in and got fouled [in Game 1]. We have a number of clips over the years of him rebounding over the top in traffic where no guard can get that ball.
"He brings a contagious element to our team that you can try all you want to quantify it, but other than winning and losing, you can't quantify it."
Here's all you need to know about Smart's flare-up with Simmons: The Celtics were up 19 points with 1:44 to go when it occurred. Smart's competitive juices never stop flowing.
Smart took umbrage when Simmons twice struck Smart in the head with an elbow as the two jockeyed for position for a rebound. Smart got whistled for a loose-ball foul when he delivered a two-handed shove that sent Simmons staggering backward.
As Simmons walked toward midcourt, Smart started barking at the rookie and stalked after him. Celtics assistant coach Jay Larranaga, who is Smart's individual coach and knows him as well as anyone, saw what was happening and launched off the bench, fought through an unintentional screen by Stevens, and broke into a sprint before bear-hugging Smart to ensure no further escalation.
Cooler heads might have prevailed, but the Celtics weren't taking any chances. Smart is much too valuable for Boston to risk losing, especially as it navigates the postseason without the services of Kyrie Irving, Gordon Hayward and Daniel Theis.
One of the primary keys for Boston in this series against Philadelphia is limiting the output of Simmons. In Game 1, the Celtics put some of their most stout big men on the rookie with Marcus Morris, Horford, and Semi Ojeleye defending on 52 of the 82 possessions that Simmons was on the floor, according to Second Spectrum data.
Most teams don't even think of committing a guard to Simmons. But Smart is not your typical guard. Smart defended Simmons on 17 possessions and the rookie did not score while missing his only attempt, and turned the ball over once.
What's more, Simmons didn't generate an assist on those possessions and the Sixers scored only eight total points as a team (by comparison, the Sixers scored 27 points in the 18 matchups when Simmons was defended by Horford and 27 points in the 23 matchups against Morris, per Second Spectrum data).
With Jaylen Brown sidelined by a hamstring strain, Smart's more frequent assignment was to chase around JJ Redick for much of Game 1. Smart defended Redick on 30 of his 65 total possessions, according to Second Spectrum data, and held Redick to a modest eight points on 2-of-7 shooting. Redick missed all five of his 3-point attempts when defended by Smart but made the only two he otherwise attempted in the game.
"There is a complete competitor and there is a pit bull," Sixers coach Brett Brown said of Smart. "He's just physically imposing and he has a mindset and disposition to back it up."
All of TD Garden seemed to groan as Smart went up to shoot a 3-point attempt early in the third quarter of Monday's Game 1.
Smart hadn't just missed all five shots he took in the first half, he hadn't made a 3-pointer (0-for-11 to that point) in the 14 quarters since returning to action. Heck, he hadn't made a shot outside of 15 feet in that span.
But with Dario Saric all but begging Smart to shoot, he obliged -- with an unnecessary step-back maneuver, no less, considering that Saric was about eight feet in front of him.
Smart went on to score all nine of his points in the quarter as Boston prevented Philadelphia from making any sort of charge.
Smart, his right shooting hand bandaged to protect his thumb, is having a cringeworthy offensive postseason since returning from injury. Of the 102 players with at least 40 possessions finished through Tuesday's games, Smart is dead last while averaging 0.592 points per play, according to Synergy Sports data. No player in the top 100 is below 0.7.
Smart is shooting 12.5 percent from beyond the 3-point arc and 25.7 percent overall. But he has quietly dished out 15 assists over the past two games and his ballhandling abilities have taken some of the playmaking stress away from backcourt partners like Terry Rozier.
While casual fans tend to obsess about Smart's abysmal shooting numbers, Stevens countered with the perspective of those closest to the game.
"I've never had a coach from another team say anything but, 'That dude's a total winner.' Ever," Stevens said. "When you watch him play on film, I think it's pretty obvious. He's a guy that you know impacts the game."
Stevens says he believes Smart is still shaking obvious rust from the six-week layoff. But it's hard to argue with what he's doing defensively. The Celtics are allowing 102.2 points per 100 possessions in Smart's 115 minutes of floor time. That number spikes to 109.0 without him.
More important, Smart is making all those 50/50 plays. It's why the hashtag #winningplays trends most game nights in Boston.
One night he's blocking Giannis Antetokounmpo at the rim and making assists from the ground with three Bucks trying to pry the ball loose, the next night he alternates between chasing Redick around the perimeter then goes inside and jousts with Simmons and Embiid.
As Jaylen Brown put it: "When [Smart is] on the floor, we're a better team."
Smart admits it has been a wild couple of months. Basketball, as it always was during an often tumultuous childhood, remains a sanctuary for him. And he's never taken any of this for granted.
"To say I appreciate it more, I can't say that," Smart said. "But I can definitely understand why I appreciate it the way I do because, at any given moment, you never know what could happen."
Even when the season ends, things won't calm much for Smart. After contract extension talks fizzled early in the season, he's set to wade into restricted free agency, and it will be fascinating to see what kind of offers he receives from teams and whether they can look past his stat line.
The Celtics and Smart talked about a possible extension before October's deadline but nothing came of it. President of basketball operations Danny Ainge said at the time that he expected Smart to respond with the best season of his career and, while Smart's numbers didn't change all that much from a year ago, his impact on Boston's success remained undeniable.
The lingering question is, given Smart's tough-to-quantify impact, would another team be willing to pay big money to lure him away?
Sitting over the cap, the Celtics won't have much beyond the midlevel exception to seek (or retain) impact talent this summer. But with Smart's rights, Boston could splurge a bit to keep the gritty guard in green. Even more beneficial for Boston would be if Smart elected to simply sign his $6 million qualifying offer and explore unrestricted free agency in the summer of 2019.
For Smart, it might be tough to find suitors this summer as a restricted free agent. A handful of teams could offer the midlevel exception ($8.6 million for teams with cap space) but Boston would still have the opportunity to match or exceed those offers.
The Celtics could go a bit higher than the market -- in the $10 million to $12 million range -- with a length conducive to both sides. One additional benefit for Boston if it does spend to retain Smart, it gives the team a tradable contract in a range it doesn't reside as the Celtics have big money committed to its Big Three of Hayward, Irving and Horford -- the next highest deal on the books for next season is Jayson Tatum's bargain rookie deal of $6.7 million.
Things get a bit trickier for a Boston team lingering near the tax line if a team put in a monster offer for Smart.
It's also fair to wonder if there's enough room for all these guards once Irving is healthy and with Rozier emerging. But, if this season has reminded Boston of anything, it's that too much depth is rarely a problem. And Stevens has a way of making sure he finds enough minutes for all his guys.
But there are more pressing concerns now for Smart. On the court, he's three wins away from a return to the conference finals. Off the court, his mom is improving in her battle with cancer but there's still a long road ahead.
"She's still fighting," Smart said.
So is he. And that's what makes Smart so unique.