Mace's CFL rights were traded by the Toronto Argonauts on August 22, 2010, in exchange for non-import linebacker Tristan Black.

He recovered a fumble and returned it 60 yards for a touchdown in Calgary's October 17 victory in Saskatchewan.

[10] Mace suffered a torn shoulder labrum in Week 1 of the 2013 CFL season which caused him to undergo season-ending surgery.

[9] He played in both of the Stamps post-season games, knocking a pass down in the West Division Final,[9] and recording a sack in Calgary's win in the 102nd Grey Cup.

[9] His community initiatives have included starting a holiday turkey and ham drive for food banks and charitable groups, and launching Mace's Faces, which allows 15 at-risk youth to attend every Stampeder home game.

[15] On January 6, 2022, it was announced that Mace had joined the Toronto Argonauts as the team's defensive coordinator.

On November 29, 2022, it was reported by TSN insider Farhan Lalji that Mace was one of three finalists for the vacant Ottawa Redblacks head coaching job.

[17] On November 29, 2023, TSN reported that Mace had been named as the new head coach of the Saskatchewan Roughriders.

The Roughriders officially announced him as the team's 48th head coach in club history on November 30, 2023.

[18] In his first season, he led the team to a 9–8–1 record and a home playoff game following a two-year post-season drought, but lost to the Winnipeg Blue Bombers in the West Final.