MacKinnon sustained a lower-body injury and won't return to Thursday's game versus the Senators.
MacKinnon was hurt in the second period and ruled out at the start of the third. The superstar center was held off the scoresheet for the third time in his last four games prior to his early exit. Cale Makar (lower body) was also injured in the contest, leaving the Avalanche's roster in crisis mode ahead of Saturday's game in Montreal.