Rask left just 1 minute, 12 seconds into Tuesday night's game after getting hit in the head by a passing Blue Jackets player. Emil Bemstrom was cutting across the front of the Bruins' crease when it appeared his elbow or forearm caught Rask on the side of the head.
The hit drew the ire of Bruins coach Bruce Cassidy.
"It was an elbow to the head. It's a penalty is what it is, so you have to move on," Cassidy told reporters afterward. "It's just unfortunate that it happens to your No. 1. It was pretty clear to me."
Rask's injury came a day after he decided to skip the All-Star Game, choosing instead to take that Jan. 24-26 weekend for self-care.
Rask, 32, has appeared in 28 games this season, after leading the Bruins to the Stanley Cup Final last season, appearing in a combined 70 regular-season and playoff games.
Jaroslav Halak, who stepped in for Rask and made 24 saves Tuesday, got the start Thursday night against the Penguins and stopped 29 of 30 shot attempts in a 4-1 win.
Information from The Associated Press was used in this report.