Coach Ted Nolan said following practice Monday that McCormick is recuperating at home. Nolan called it a good sign, but cautioned there is no timetable for the player's return.
McCormick was hospitalized over the weekend after the clot was discovered. He scored his first goal of the season in a 2-1 loss at Tampa Bay on Friday.
The Sabres called up forwards Phil Varone and Zac Dalpe from their AHL affiliate in Rochester.
Dalpe has yet to play for the Sabres since signing with the team last summer. Varone is back in Buffalo after playing three games last week.
Buffalo hosts Detroit on Tuesday night.