Stanley played as a youth with the Waterloo Wolves in the AHMMPL, before he was selected in the first round, 12th overall in the 2014 OHL Priority draft by the
Windsor Spitfires. On May 9, 2014, Stanley committed to the Spitfires of the OHL to play under
Bob Boughner. Stanley has also been involved with IIHF tournaments and development camps. On December 7, 2016, Stanley was signed to a three-year, entry-level contract with the
Winnipeg Jets. During the
2016–17 season, Stanley injured his knee in January and did not return to the lineup until April. On May 28, 2017, Stanley won the
Memorial Cup Championship with the Windsor Spitfires. On August 8, 2017, Stanley was traded to the
Kitchener Rangers. Despite his trade, Stanley was awarded the Scott Miller Extra Mile Award by the Spitfires at the end of the season. Due to his success, Stanley was invited to the Winnipeg Jets training camp before the
2017–18 NHL season, however, he failed to make the roster and was sent back to the OHL. During the
2017–18 OHL season, Stanley received a two-game suspension for head-checking
Akil Thomas during a game against the
Niagara IceDogs. The Jets assigned Stanley to the Manitoba Moose after the Rangers were eliminated from the 2018 OHL playoffs. After attending the Jets 2018 training camp, Stanley was reassigned to the Manitoba Moose to begin his first professional season. After finally cracking the Jets lineup for the 2020–21 NHL season, Stanley achieved a couple of career milestones in his rookie season; he had his first career fight on March 24, 2021, against
Zack MacEwen of the Vancouver Canucks, and would later score his first NHL goal on March 27, 2021, scoring on
David Rittich of the Calgary Flames in a 4–2 Jets loss. On August 4, 2021, the Jets re-signed Stanley to a two-year, $1.8 million contract. On August 19, 2023, the Jets re-signed Stanley to a one-year, $1 million contract. On July 6, 2024, the Jets re-signed Stanley to a two-year, $2.5 million contract. On March 6, 2026, Stanley was traded to the
Buffalo Sabres alongside
Luke Schenn, in exchange for
Jacob Bryson,
Isak Rosen, a conditional
2026 fourth-round pick, and a
2027 second-round pick. ==International play==