He is a two-time CFL All-Star and a three-time Grey Cup champion after winning with the Calgary Stampeders in 2018 and with the Argonauts in 2022 and 2024.

[4][5] On December 23, 2016, the 49ers promoted McManis to their active roster from their practice squad after placing Torrey Smith on injured reserve.

[3][10] He made his CFL debut in week 3 on July 8, 2017, against the Winnipeg Blue Bombers, where he had two defensive tackles and two sacks.

[12] He also made his post-season debut, playing in two games, including the 106th Grey Cup, where he had two special teams tackles and one fumble recovery in the Stampeders' 27–16 victory over the Ottawa Redblacks.

[12] In the 2019 season, McManis became a regular starter where he played and started in 15 regular season games, recording 86 defensive tackles, nine special teams tackles, four pass knockdowns, two sacks, one forced fumble, and one fumble recovery.

[12] After the CFL canceled the 2020 season due to the COVID-19 pandemic, McManis chose to opt-out of his contract with the Stampeders.

[12] In the East Final against the Montreal Alouettes, McManis recorded one defensive tackle but suffered an arm injury during the game.

[24] McManis started in all three post-season games, including the 111th Grey Cup where he had six defensive tackles and one interception in the Argonauts' 41–24 victory over the Winnipeg Blue Bombers.