Billy Gneiser never saw his grandfather play. He is just 13, after all, and Stan Mikita’s career ended 38 years ago. Billy has scoured YouTube but hasn’t been able to find many clips of Mikita’s powerful stride, his famously curved wooden stick, his unparalleled vision and shot.

“All I know is he was pretty good,” Billy said.

But Mikita’s image is etched all over Billy’s face — the same eyes, the same nose, the same broad smile. His legend has been taught to Billy over the years — when he sees someone in a No. 21 red sweater, when he hears longtime Blackhawks fans talk about his greatness and his kindness, when he stepped onto the ice for the national anthem with two of his brothers, Charlie and Tommy, Friday night, representing Stan for his “One More Shift.”

But Mikita’s legacy is more tangible to Billy than a face in the mirror or a kind word from a stranger. Before Lewy body dementia robbed Mikita of his memories and his self, he taught Billy everything he knows about hockey.

Stan even told Billy to switch positions to the one that allowed him to post 541 goals and 926 assists in 1,394 NHL games, to become an eight-time All-Star, to become the only player ever to win the Hart (MVP), Art Ross (scoring leader) and Lady Byng (gentlemanly play) trophies in the same season. He accomplished that last feat twice, in 1966-67 and 1967-68.

“I was a defenseman at first, and I was like, I want to score more goals,” Billy said. “So my grandpa said ‘Be a centerman, you’ll score more goals like that.’ I’ve been a center since.”

That Mikita, the one who lit up scoreboards and lit up fans’ faces for 21 seasons, doesn’t exist anymore. His daughter, Jane, and other family members still visit him in a long-term care home just about every day, but he doesn’t recognize them. Billy said it is hard to remember the grandfather he once knew, because of “the way he is now.”

“Stan is from the neck up, completely gone, and from the neck down, he is as strong as a horse,” his daughter, Jane Mikita Gneiser, said. “He is just kind of plugging along.”

Mikita’s caretaker was planning to show him Friday’s pregame ceremony, and it is impossible to know if it would register with him that he was being honored, that his grandchildren were skating in his place, in his jersey. But Jane was hopeful, noting that he “kind of perked up” with relatives flying in from out of town for the ceremony.

“Every now and then, he’ll have those moments where you go, ‘Oh, man, he gets it, he understands,’ ” Jane said. “But he does not know us for the most part.”

Mikita was welcomed back to the Hawks organization in 2008, and left a lasting impression on the core members of the team’s championship era.

“The more time you spend in a city like Chicago, you get to know fans who’ll come up to you and tell you stories about the days that he played, and growing up watching him,” Jonathan Toews said. “You also start to hear those stories about who he was away from the rink and realize it’s so much more than that.”

Gneiser’s primary concern Friday night was not falling down while skating, an unlikely problem for a member of the Romeoville Huskies, a bantam team. But the meaning of the evening was not lost on him.

“Everybody that I see talks about my grandfather,” he said. “They said, ‘Oh, I used to watch your grandfather, he was a great man off the ice, a great man on the ice.’ . . . I’m trying to follow his footsteps, on and off the ice.”