Foerster was lauded by Philadelphia Flyers general manager Daniel Briere as "a big piece and part of our future" after signing an eight-year, $56.8 million contract (average annual value of $7.1 million) with the Flyers on July 1, 2026.

At age 24, Foerster was entering the final season of a two-year, $7.5 million contract ($3.75 million AAV) he signed May 29, 2025. He was leading the Flyers with 10 goals in 21 games through the 2025-26 season when he sustained an injury to his right arm Dec. 1, and surgery Dec. 15 sidelined him until April 2. He had four points (three goals, one assist) in eight games when he returned, and his goal in the fourth round of a shootout against the Carolina Hurricanes on April 13 clinched the Flyers their first Stanley Cup Playoff berth since 2020.

Foerster was selected by the Flyers in the first round (No. 23) of the 2020 NHL Draft. The native of Alliston, Ontario played junior hockey for Barrie in the Ontario Hockey League, where he finished with 52 goals and 114 points in 139 games. During the 2019-20 season, he led the OHL with 18 power-play goals.

From 2020-23, Foerster played for Barrie, Lehigh Valley of the American Hockey League and the Flyers. He helped Canada win gold at the 2022 IIHF World Junior Championship with six points (three goals, three assists) in seven games and had three points (two goals, one assist) in seven games at the 2025 IIHF World Championship.

Foerster enjoyed a breakout season in the NHL with 43 points (25 goals, 18 assists) in 81 games. He made his NHL debut against the Hurricanes on March 9, 2023, and scored his first NHL goal in his fourth game against Carolina on March 18.