"The doctors want no blood on his eye before he plays," Red Wings general manager Ken Holland said Wednesday.
"It's a blow because he scored 30 goals this season, and he's one of our key players. But we expect to get him back at some point in the series, and that's good news for us and him."
Calgary's Craig Conroy hit Holmstrom with his stick at 6:44 of overtime Sunday night in Detroit's series-winning victory over the Flames. The 34-year-old left-winger had 30 goals and 22 assists during the regular season.
Defenceman Brett Lebda is day to day with a sore ankle and concussion. He hasn't played since Saturday when he twisted awkwardly into the boards while checking Daymond Langkow.
Lebda was called for tripping, and Langkow punched him in the face while both were on the ground. He played in 74 games for Detroit during the season. He recorded five goals and 13 assists.