Father knows best: Justin Tatum took his own approach with his son before Jayson Tatum dominated the 76ers in Game 7

Jayson Tatum needed to relax to improve on his Game 6 struggles, and his dad knew that.Jim Davis/Globe Staff

Legacies are built on games such as these, and Jayson Tatum was fully aware of that fact. His resurrection in the final four minutes of Game 6 against the Philadelphia 76ers saved the Celtics season. Now he needed brilliance for the full 48 in Sunday’s Game 7.

The moment was not too big for Tatum, as it appeared for most of Game 6. The first-team All-NBA forward, the Celtics franchise cornerstone, one of the most gifted players of his generation, ignored the voices that stressed the importance of this opportunity and instead concentrated on trusting his skills and his mental approach.

While the repercussions of losing this game were monumental, Tatum ensured that there would be no suspense for the outcome with the best stretch of basketball in his six-year career. He put his teammates on his once-bony, but now broad, shoulders and carried the Celtics to the Eastern Conference Finals with a masterpiece 51-point performance.

Tatum’s scoring relegated the once-mighty 76ers into the Five Stooges on the floor as the Celtics ran away with a 112-88 win in front of a sold-out TD Garden that included a rare visit from Tatum’s father, Justin.

Justin said he watched his son struggle to a 1 for 13 start in Game 6 from his St. Louis home, changing clothes five times during the game to help improve Jayson’s luck. The last outfit worked as Tatum scored 14 of Boston’s final 16 points for a crucial win at Philadelphia.

Three days later, Tatum punched first, scoring 11 points in the first period and then another 14 in the second. For the first time since Game 1, his 3-point shot was falling and that opened up all other aspects of his game. He attacked the rim fearlessly, drew fouls, and drained jumpers.

Tatum understood his basketball reputation would soar or plummet from this one game, but he spent the past few days seeking normalcy.

Eighteen of Tatum's 51 points Sunday came on threes.Jim Davis/Globe Staff

“It was definitely on my mind that I had played as bad as it could get for 43 minutes,” Tatum said of Game 6. “Going into Game 6, I was too, it sounds crazy, but I was too locked in. I was too tight; too much in my own head thinking what do I need to do? How many points do I need to score? It’s a big moment. [Sunday] I was more myself. Pregame, I was relaxed, laughing, joking, and that’s when I play my best when I’m having fun. This is basketball. This is something I’ve been doing since I was a kid.

“Just not think about the pressure and what everybody is going to say. Just focus on the game.”

Justin was his son’s first coach and pushed him to greatness, so much so that Jayson told Justin to temper his criticism as he grew older. As Jayson has ascended into an NBA All-Star, Justin has become more of a confidant and friend.

While he attended a handful of playoff road games, Justin decided to come to Boston for the first time as a means of support, win or lose.

“It was satisfying because I know how much pressure he puts on himself to want to get out of this series and win another chip for Boston,” Justin said. “For him not playing well in the previous games until today, it was just satisfying to see that ball go in the hole.”

Justin said Tatum restored his confidence once he hit a step-back jumper in the face of Joel Embiid with four minutes left in Game 6. He noticed Jayson walking with more pep, rising first after timeouts. The swagger was back.

“When he does things like that, it’s very noticeable to me because I know who he is,” Justin said. “He was a man on a mission [in Game 7]. [On his first basket] he gave Embiid the first pump fake and drove [for a dunk] and expressed himself.”

Instead of being the umpteenth person to emphasize the importance of Game 7 and the impact on his son’s legacy, Justin said he texted his son on Saturday to talk about normal life stuff. He’s learned the perils of being the overbearing parent-coach. He trusted that his son would be prepared for his moment.

“I said, ‘I know you’re getting it from everywhere,’ ” Justin said he told Jayson. “I just want to have a normal conversation. Just keep having fun and we’ll talk about something else and then we’ll integrate to what [he needs] to do. It’s not like hearing the same rhetorical things from outsiders. [Jayson’s thinking] ‘I need to hear the voice that I’m used to and not talk about the same [expletive] that I’ve been hearing from everybody else.’ So I just use a different approach.”

Instead of pondering the pressure, Tatum said he reflected on his basketball roots, thinking about those days when he played the game all day for free, those times when a rail-thin, baby-faced Tatum worked feverishly on his moves, fantasizing of days like this.

”When you think about those days when you were a kid at the YMCA or whatever, the game kind of opens up,” he said. “Just try not to think about the pressure or what everybody is going to say. Just focus on the game.”

And finally, Tatum got caught up in the moment. When he drained a long 3-pointer during a 33-5 third-quarter run, Tatum embraced the raucous crowd, walked past the mid-court logo, pointed to the floor and said, “This is my [expletive].”

He overcame the pressure. He returned to his old self. He declared his love for the game, and for his franchise and the crowd.

“I’ve been here my whole career and I feel they embrace me as one of their own,” he said. “That means a lot. I love being here. I love getting to put on this uniform and I love to play big games and put on big performances in front of them.”