BOSTON — Bradley Beal has seen plenty of impressive performances from Jayson Tatum on a basketball court since the two were kids growing up together in St. Louis.

But after Tatum scored 50 points to lead his Boston Celtics past Beal’s Washington Wizards with a 118-100 victory Tuesday night, giving Boston the seventh seed and a date Saturday night with the Brooklyn Nets in the first round of the NBA playoffs, Beal said there was nothing the Wizards could do to stop him.

“It didn’t matter who was in front of him,” said Beal, whose Wizards will head back home to face the Indiana Pacers in a winner-takes-all game for the eighth seed Thursday night. “That is something I have been trying to tell his ass for years. It’s tough when you guard him. He’s 6-9, he can get his shot off, he’s strong and can shoot the ball.

“He’s a three-level scorer. So you got to respect everything he does on the floor. I know a lot of his moves, and a lot of it I was there, but I am only 6-3. I wish I was 6-9 with robotic arms.

“He’s a special talent, and I have been saying that since he was in diapers. It doesn’t surprise me.”

It was a scintillating all-around performance from Tatum, who reached 50 points for the third time in six weeks. He also went 17-for-17 from the foul line, to go along with eight rebounds, four assists, a steal and two blocks in 41 minutes. That also included a 23-point explosion in the third quarter that put Boston back out in front for good.

“I don’t know,” Tatum said when asked if performances like this one have officially pushed him into the game’s superstar class. “I guess it helps. I don’t really get caught up in those who think I’m a superstar and those that don’t. What does that really mean? I know that my teammates, I’ve earned their respect. I’ve earned the respect of the guys I’ve played against and the coaches.

“I believe in myself, and that’s all that matters.”

Tatum nearly outscored the Wizards by himself in that third quarter (26-23), as the Celtics opened the second half with a 20-4 run. That, coupled with a 10-4 push to end the first half, turned what had been an eight-point lead for the Wizards into a 16-point cushion for Boston.

And while the Wizards made a couple of pushes to get back into the game early in the fourth quarter, the Celtics had an answer every time, usually coming from either Tatum or Kemba Walker, who had his own impressive 29-point performance to help carry Boston into a meeting with Brooklyn and old friend Kyrie Irving.

“We’ve been through a lot, and so we’re hardened in a lot of ways,” Celtics coach Brad Stevens said. “We’ve been backs against the wall most of the year and [had] to play tonight to get into the playoffs just to earn the right to play probably the most talented team that’s been assembled since I’ve been in the NBA.

“It takes a lot of effort, it takes a lot of togetherness and it takes staying together through tougher times. We’ll get ready for Brooklyn starting Thursday when we get back together. We know that challenge. Those guys are the best of the best, and going into that, if I’m a fan and just a general fan of the NBA, I have a hard time seeing them lose. So we’re going to have to play great, we’re going to have to play great together and we’re going to have to be really, really sound on both ends of the floor.”

It has been a season full of ups and downs for the Celtics, who have dealt with a revolving door of players in and out of the lineup because of both injuries and COVID-19. That includes All-Star Jaylen Brown, who is out for the remainder of the season after undergoing wrist surgery last week.

But Tuesday night’s game was a reminder of what Boston, which has made the Eastern Conference finals in three of the past four seasons, is capable of when it’s clicking.

Those moments, however, have been few and far between this season. That’s how the Celtics wound up in the play-in tournament in the first place and why they will go into this first-round series with the star-studded Nets as a massive underdog despite their own talent and recent playoff pedigree.

“Study, preparation — I think the preparation is key,” said Celtics big man Tristan Thompson, who finished with 12 points and 12 rebounds in 30 minutes off the bench behind starting center Robert Williams, who left the game early in the second half with a recurrence of a recent battle with turf toe. “If you can prepare for your opponent better than they can prepare for you, mentally put yourself in that mode, I think that’s how you try to gain an edge. We know how talented this Nets team is. So for us, our preparation is going to be key.

“Guys gotta watch film. KYP — know your personnel. Know the guy you’re matched up with, knowing their tendencies, knowing what moves they like to go to, because those little things count in the playoffs. Every possession counts. So whether it’s [James Harden] ISO-ing to a step-back when he has the ball in his right hand, or Kyrie ISO-ing to the sidestep from the right wing, or [Kevin Durant] when it’s in his left hand for the pull-up or right hand to the drive, you’ve got to know that stuff going into the game because those little possessions can determine the game.”

Against a team full of stars, it also helps if you have some of your own to fight back with. With the way Tatum and Walker, in particular, played Tuesday night, Boston will head into its series with Brooklyn hoping to see more of the same against the team favored to win this year’s NBA title.

“Obviously, it’s going to be tough without [Jaylen],” Tatum said. “We know how good of a team they are. Everybody knows the guys that they have over there.

“But I’m excited to get this opportunity to be in the playoffs. It’s my fourth year in a row. I don’t take that for granted. Myself and everybody else, we’re excited. It’s the playoffs, so we just have to get ready for the next game.”