The Sixers’ Matisse Thybulle is a remarkable defender. His secret starts with his dad and a swimming pool. | Mike Sielski

In the 76ers’ family suite of the Wells Fargo Center, Greg Thybulle felt a father’s fierce pride rise within him Wednesday night as he once again watched the subtle ways that his son could dominate a basketball game without ever having to score. There was Matisse Thybulle, sprinting to block a three-point shot by Davis Bertans — 6-foot-10 Davis Bertans, five inches taller than Matisse. There he was, batting the ball out of Ish Smith’s hands from behind. There he was, going straight up to snuff out a jumper by Rui Hachimura, who is 6-8.

“I wasn’t surprised,” Greg said over the phone later that night. “He plays old-school defense.”

Has anyone done it better in a single game? No NBA player had collected at least four steals and blocked at least five shots in 20 minutes of action until Thybulle did it in the Sixers’ 120-95 Game 2 victory over the Wizards. No NBA player had packed so much great defense into so short a period of time. Ben Simmons was pushing the Wizards around in the post and Joel Embiid was one-legging three-pointers Wednesday. But Thybulle was the true marvel in the rout, and he is the Sixers’ prospective X factor in the later rounds of this postseason, where they might encounter Trae Young. Or Giannis Antetokounmpo. Or Kevin Durant and James Harden and Kyrie Irving all at once.

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The reason to think that the Sixers can reach the NBA Finals, and win their first championship since 1983, is that they are as versatile or more than any team in the league, that they can win in multiple ways. Embiid might score 40. Or Tobias Harris, Seth Curry, and Danny Green might hit shot after shot from 19 feet and farther. Or the Sixers, the league’s second-best defensive team this season, might smother an opposing offense, and Thybulle would likely be at the center of such a clampdown.

During the regular season, he averaged 1.6 steals, the ninth-best mark in the NBA, despite playing just 20 minutes a game — six minutes less than any other player in the top 20. He blocked 1.1 shots per game, the highest average of any guard in the league. Twice at the University of Washington, he was named the Pac-12 defensive player of the year, and as much as Sixers general manager Elton Brand telegraphed his willingness to trade up in the 2019 draft to get Thybulle — he gave up two picks to get him — the move more and more seems a masterstroke. Just as another coach might call on a scorer off the bench to inspire his team or change a game’s momentum, Doc Rivers often sends in Thybulle to do the same thing at the opposite end of the floor.

“I guess you can say he’s our defensive Lou Williams,” Rivers said. “Lou Williams, I had, and I had Jamal Crawford, both offensively, where you threw them in and you told them if they passed the ball once, you were going to take them out. Their job was to score. Tisse’s job is to get stops when he comes in. Tony Allen, I guess, way back [with the Celtics] was very similar because he was coming off the bench for us. Offensively, there are a few guys like that in the league, and the guys who they are, are usually the sixth man of the year.”

Thybulle, 24, won’t ever win the award for his offense, in large part because when he began playing basketball, in grade school, his father preached a different sermon to him: Don’t worry so much about scoring. Defense — that’s where you can shine. Through his first few years in the sport, though, the kid didn’t want to listen. “I was dealing with a teenager,” Greg said, “and teenagers go through a phase where they don’t believe their parents can breathe and walk at the same time.” So Greg, a mechanical engineer and corporate manager with Hewlett Packard who at the time knew little about basketball, built a greater measure of credibility with Matisse by becoming a high school referee. He’d chat up coaches, asking them what they looked for in a player.

“They all had the same wish: ‘If only I had a guy who would play defense, he would be on the floor right now,’” Greg said. “Defense is more forgiving than offense. On offense, you have to put it in the basket. On defense, I just have to shut you down to 50 or 75 percent, and I’m a hero.”

It took Matisse until he entered Skyline High School, in Sammamish, Wash., before he acknowledged that his father’s thinking made sense and started to follow it. “For whatever reason, I had a knack for it,” said Matisse, who had two steals and two blocks in Game 1 against the Wizards. “It just all fell into place.” In his first varsity game, as a freshman, Thybulle guarded Bothell High’s best player: Zach LaVine, now a star for the Chicago Bulls. He stole the ball from LaVine twice and blocked two of his shots.

“It was a watershed moment,” Greg said. “All of a sudden, it went from rain to sunshine.”

What Matisse quasi-dismissed as his “knack” was actually a set of circumstances and skills that have combined to shape him into an elite defender. The Thybulle family lived in Sydney, Australia, for seven years, and Matisse spent much of his childhood adhering to the culture of the country, rising at 5 a.m. for his daily swimming lesson. Those laps in the pool, his father agreed, allowed Matisse to develop an internal clock in his head — stroke … stroke … I’m coming up to the turn … now — that he uses to this day, noticing whenever an opposing team has five seconds or less remaining on the shot clock, reacting and freelancing accordingly.

“He knows that, at five seconds, whoever has the ball last is going to shoot,” Greg said. “There’s not going to be another pass. That’s one of the many actions he does instinctively to come up with a block.”

There are others. As a referee, Greg could advise Matisse on the best and most reliable ways to guard or harass an opposing player without fouling, and whenever he happened to be officiating one of Matisse’s games, he could help him refine his defensive technique. “I was tough on him, man,” Greg said. “He’d just look at me wrong, and I’d call a foul.” Now Matisse knows, when a player lifts off for a shot, not to jump directly at him, but to the side of him. Not where the player was, but where he will be.

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“He has catlike reflexes,” Greg said, “and he was built — I can’t say it enough — for defense. Matisse’s personality is one that says, ‘I will always, always, make my teammates look better.’ That’s what he does. That’s what defense brings out. That’s why all four guys want Matisse on the floor. They know he’s going to get the ball in their hands.”

If that requires taking the ball out of an opponent’s, all the better. It was what Matisse Thybulle was born to do.