Petry is a puck-moving defenseman who can play heavy minutes - just what the Montreal Canadiens wanted when they acquired him from the Edmonton Oilers in a trade on March 2, 2015.

Born in Ann Arbor, Michigan, and raised in nearby Farmington Hills, Petry was reared in a sports-minded family. His father, Dan, pitched for 13 seasons in Major League Baseball, winning 125 games and helping the Detroit Tigers win the World Series in 1984.

While playing with Des Moines of the United States Hockey League, Petry caught the eye of Edmonton Oilers scouts. With Edmonton looking to revamp its defense, the Oilers selected him in the second round (No. 45) of the 2006 NHL Draft. His hockey education continued at Michigan State University, where he played in every game during his three seasons.

Petry turned pro in March 2010, spending time in the American Hockey League before making his NHL debut for the Oilers on Dec. 28, 2010, getting an assist in a 4-2 loss to the Buffalo Sabres. His best season with the Oilers was his first full one, 2011-12, when he had 23 assists and 25 points in 73 games.

On March 2, 2015, Edmonton traded him to the Canadiens, with whom he played the final 19 games of that season, scoring seven points. Petry added two goals and an assist in 12 Stanley Cup Playoff games in 2015.

As an unrestricted free agent, he signed a six-year contract to stay with the Canadiens on June 2, 2015. In his first full season in Montreal, Petry had 16 points (five goals, 11 assists) in 51 games, and signed a four-year contract (average annual value of $6.25 million) Sept. 25, 2020.

Petry became a mainstay on the Montreal defense, increasing his production in each of the next three seasons, until he was traded to the Pittsburgh Penguins on July 16, 2022. The Penguins included Petry in the three-team trade with the San Jose Sharks and Canadiens that brought him back to Montreal and sent defenseman Erik Karlsson to Pittsburgh on Aug. 6, 2023. Petry was then traded to the Detroit Red Wings by the Canadiens on Aug. 15 for defenseman Gustav Lindstrom and a conditional fourth-round pick in the 2025 NHL Draft.

Petry joined the two-time Stanley Cup champion Florida Panthers when he signed a one-year contract for the 2025-26 season. He skated 11:44 and was plus-1 in his 1,000th NHL regular-season game, when Florida defeated the Vancouver Canucks 8-5 at Amerant Bank Arena on Nov. 17, 2025. He was traded to the Minnesota Wild on March 5, 2026.