Maxey, the second-year Philadelphia 76ers guard, is showing a maturity beyond his 21 years during the playoffs. And the Sixers need him.Many of the key members of the Philadelphia 76ers have become jaded by the realities of life in the N.B.A.Their mettle has been questioned at times, even though they have collectively played professional basketball for decades. Sometimes their ability and their durability have been questioned, too. They approach the season with a guarded demeanor that offers little hint of the joy they might find in the game they play for a living.Then there’s Tyrese Maxey.He laughs. He giggles. His most common facial expression is a smile. He teases his teammates.On the court, though, Maxey’s play betrays little of that. On a team with veteran stars and a coach who all have something to prove, Maxey is a linchpin whose steady play has given cover for the team’s lapses every once in a while.On Sunday night, the 76ers did not need a heroic performance from Maxey to tie their best-of-seven second-round playoff series with the Heat at two games apiece, even as Miami’s Jimmy Butler scored 40 points in Philadelphia’s 116-108 win. But Maxey still made a difference in Game 4: He scored 18 points, hit all six of his free throws and helped the 76ers maximize strong performances from their stars.The Sixers’ best players — center Joel Embiid and guard James Harden — combined for 55 points, with Embiid scoring 15 points in the first quarter, Harden scoring 13 in the second, and both making important plays as the game wound down. Harden’s 18 second-half points included four 3-pointers.Maxey has established himself as part of the team’s engine.Maxey opened the playoffs with a 38-point game against the Raptors, and he averaged 21.3 points per game for the first-round series.Nathan Denette/The Canadian Press, via Associated PressThe 76ers are driven by their stars, but when the stars are limited by injuries or the ebbs of the game, Philadelphia has been able to count on Maxey. This was his second season in the N.B.A. and first as a full-time starter. He was an occasional part of Philadelphia’s starting rotation last year, and played limited minutes in the 2021 playoffs.This postseason, though, he made an immediate contribution. Maxey scored 38 points in Game 1 of the 76ers’ opening-round series against the Toronto Raptors, lifting Philadelphia when Harden’s play was inconsistent.“I saw growth,” Harden said about Maxey that day. “I saw, like, from being up and down, not really having consistent minutes last year in the postseason to starting and having a huge role on a championship-contender team. He just was calm out there and took his shots when they were open. He took his attacks when they were available. He just made the right play, which he does.“He’s ultra-confident. That’s what we’re going to need going forward.”Maxey nearly had a triple-double in Game 2 of that series, with 23 points 9 rebounds and 8 assists. Philadelphia beat Toronto in six games, and Maxey scored 25 points in the clincher.His next-best playoff performance came in Game 2 against the Heat. Although it’s said that young players and role players usually shoot better at home, Maxey made 54.5 percent of his field goals and scored 34 points in Miami. Philadelphia played without Embiid for a second straight game because of a concussion and a facial injury.In the 76ers’ Game 3 win over the Heat, with Embiid back in the fold, Maxey scored 21 second-half points after not scoring in the first. He was 5-for-5 from 3-point range after halftime, and made seven of his eight second-half field goals.“I just started being aggressive,” Maxey said of his shift in the second half. “I kind of let the game come to me.”He averaged 17.5 points per game during the regular season, and is averaging 22 points per game in the playoffs while playing more minutes. The higher stakes and heavier workload — about 41 minutes per game now versus 35 minutes per game during the regular season — could prove too much for many young players. But it hasn’t been for Maxey.The 76ers have come to expect this kind of play from him, so much so that guard Danny Green referred to Maxey in the same breath as Embiid and Harden when discussing production from Philadelphia’s key players during a recent postgame interview on TNT.Maxey showed his on-court maturity late in Sunday’s game, with Philadelphia ahead by 6 and holding off Miami’s final push.Less than two minutes remained in the game when Harden missed a driving floater and Embiid grabbed the rebound and passed to Green. He got the ball to Maxey outside the 3-point arc, and Maxey surveyed the court with the kind of studied gaze that often comes more easily to veterans. He saw Tobias Harris free on the baseline clear across the court and threw him an alley-oop pass with 1 minute 40 seconds left.“He’s ultra-confident,” Sixers guard James Harden said of Maxey. “That’s what we’re going to need going forward.”Matt Slocum/Associated PressAfter the game, Maxey’s youthful exuberance was back. He conducted his postgame interview beside Harris, a forward eight years older than Maxey. Before the interviews started, Maxey joked about how he’d been sitting in the locker room thinking about life.A reporter asked a question and Harris began speaking. His voice was hoarse and Maxey jumped back in his seat. Harris laughed before continuing, later explaining that he lost his voice when he was hit in the throat.A few minutes later, something tickled Maxey so much that he covered his mouth with both hands to stifle his giggles.In those moments, it was easy to remember that Maxey is only 21 years old. That he plays beyond his years on the court has given the 76ers hints of a third star for the future. More