MacKinnon (lower body) is undergoing evaluations and treatments, according to Evan Rawal of the Denver Gazette on Monday.
MacKinnon sustained the injury in the second period of Sunday's 5-3 loss to Vegas in Game 3 of the Western Conference Finals. Despite clearly not being fully healthy, he managed to finish the game. It's unclear if he will play in Tuesday's must-win matchup, but an update on his status could come during Colorado's pregame media availability. The Avalanche face a challenging situation with a 3-0 series deficit, and MacKinnon's injury may further impede their chances of a comeback.