John Marino made the leap directly from college hockey to the NHL after being acquired by the Pittsburgh Penguins in a trade with the Edmonton Oilers on July 26, 2019.

The trade came four years after the Oilers selected the defenseman from North Easton, Massachusetts, in the sixth round (No. 154) of the 2015 NHL Draft, following his third season with South Shore of the United States Premier Hockey League.

Marino played one season with Tri-City of the United States Hockey League before moving on to Harvard University for three seasons. But after being traded to the Penguins, Marino opted to turn pro and signed with Pittsburgh on Aug. 8, 2019.

Not only did Marino make the Penguins out of training camp in the fall of 2019, he took advantage of a rash of injuries among Pittsburgh's defensemen to take a top-four role. He made his NHL debut against the Winnipeg Jets on Oct. 8, 2019, and scored his first goal at the Boston Bruins, the team he grew up watching, on Nov. 4. Despite missing four weeks with a broken cheek, Marino finished his first NHL season with 26 points (six goals, 20 assists) and a plus-17 rating in 56 games, averaging 20:15 of ice time.

Marino played two seasons for the New Jersey Devils following a trade by the Penguins. He had 43 points (eight goals, 35 assists) in 139 regular-season games before he was traded to the Utah Hockey Club on June 29, 2024.

Marino signed an eight-year, $54 million contract (average annual value of $6.75 million) with the Mammoth on July 21, 2026. His NHL career high of 36 points (four goals, 32 assists) and a plus-42 rating that ranked second among NHL defensemen helped Utah clinch a Stanley Cup Playoff berth for the first time since the NHL Board of Governors approved the establishment of a franchise in Salt Lake City on June 13, 2024. He scored his first NHL postseason goal in a 5-4 double-overtime loss to the Vegas Golden Knights in Game 2 of the Western Conference First Round.