Johnson didn't practice Sunday because of an illness, Ryan Boulding of NHL.com reports.
Johnson will accompany the Avalanche on the team's upcoming four-game road trip, so he might be ready to play Tuesday versus Calgary. He has earned three goals, 14 points, 78 blocked shots and 63 hits across 63 appearances this season. If Johnson can't play against the Flames, Caleb Jones could draw into the lineup.