PITTSBURGH — John Marino’s remarkable story will include many more chapters in Pittsburgh.

The Penguins announced Sunday that they had signed the 23-year-old defenseman to a six-year contract extension that runs through 2026-27. The deal, which has an average annual value of $4.4 million, begins at the start of 2021-22 season.

“I don’t know if it’s hit me yet,” said Marino, who will make $925,000 this season, the final year of his entry-level deal. “But it’s a pretty cool experience, just thinking about back to when you were just skating as a kid and your parents were taking you to the rink and all those sacrifices that have paid off.”

Marino got his start in hockey because his twin brother was born with bowed legs and a doctor pitched an unconventional idea, putting him on ice skates.

As a youth player in the Boston area, Marino was outshined by teammates with bigger frames and reputations and later flew under the radar at Harvard, too.

Family friend Kevin Stevens, along with fellow Penguins scout Scott Young, talked general manager Jim Rutherford into taking a chance on Marino just 18 months ago.

Then Marino became, without a doubt, the biggest surprise of the 2019-20 season.

With this deal, Marino will remain a huge piece of Pittsburgh’s future, with a chance to replace Kris Letang on the top defensive pair in a season or two.

“We are very fortunate to have a young, skilled defenseman like John in our organization,” Rutherford said in a statement. “His rookie season proved he is a top-four defenseman with great hockey sense. We were impressed with his strong defensive play and look forward to watching him develop offensively.”

This past summer, Rutherford told the Post-Gazette that he “would suspect that in a short period of time that Marino will turn into a guy in the top pairing.”

The Penguins acquired the blue-liner from the Edmonton Oilers during the 2019 offseason for a sixth-round draft pick in 2021 because Marino indicated that he would not sign with the Oilers, who picked him late in the 2015 draft.

Marino, after an impressive first training camp and preseason, quickly elbowed his way through a crowded group of veterans to earn a lineup spot. On Oct. 8, he made his NHL debut and picked up his first career point 18 days later.

A month into the season, he was already logging more than 20 minutes a night. He scored one of the season’s more memorable goals, burying a breakaway in his first NHL game back home in Boston. At season’s early end, he had six goals, 20 assists and a team-high plus-17 rating in 56 games.

Marino had one assist and a minus-1 rating in the team’s four playoff games.

During the playoffs in August, Letang, who has two years remaining on his contract, praised Marino for his poise, saying his play all year was “incredible.”

“He’s been a really important part of our team. He plays a lot of minutes and in a lot of situations,” Letang said. “He’s a really calm and poised guy. He has all the tools that a player can ask [for]. He’s just going to get better and better.”

The 6-foot-1, 181-pound defenseman finished eighth in Calder Trophy voting and was edged out for a spot on the league’s All-Rookie team by a pair of exceptional blue-liners in Colorado’s Cale Makar and Vancouver’s Quinn Hughes. But in a short period, he showed Pittsburgh he was a keeper.

When Marino turned pro, he believed he could play right away for the Penguins. But how did he earn a big role and a big payday so quickly?

“It’s just trusting your game,” he said. “Obviously, there’s so many factors that go into it — coaches, how you progress in the offseason throughout all the skates, learning from your teammates. There’s a lot that goes into it. But lucky enough it was all able to come together, and there’s still a long way to go.”

When the Penguins hold their first training camp practice Monday morning at PPG Paints Arena, Letang and Brian Dumoulin will remain the top defensive tandem. Marino is expected to be reunited with Marcus Pettersson on the second pair. He could also see power-play time whenever Letang sits.

If Marino’s game continues to grow, those roles may one day be reversed.

But even if this is as good as Marino will get, he is still one heck of a story.