In December 2019, he posted a 6–1–1–0 record, with a 1.98 goals against average (GAA), and stopped 222 of 238 shots for a 933 save percentage, and was named the WHL Goaltender of the Month.

[2] In April 2021, he posted a 6–0–0–1 record, with a 1.61 GAA, .936 save percentage and two shutouts, and was named WHL Goaltender of the Month.

[9] Along with John Lethemon, Cossa helped lead the Walleye all the way to conference semifinals where they eventually lost to the league's top-seeded Idaho Steelheads 4 games to 1.

[13][14] Cossa subsequently made his NHL debut on December 9, entering in relief of Ville Husso after the first period.

[15] He stopped 12 of 14 shots faced en route to a 6–5 shootout victory over the Buffalo Sabres, becoming the 11th goalie in Red Wings history to earn a win in their NHL debut.

[16] On December 1, 2021, Cossa was named to the final roster for Canada at the 2022 World Junior Ice Hockey Championships.