Grzelcyk will likely replace Connor Clifton in the Bruins lineup.
Grzelcyk was injured late in the first period of Game 2 when he was on the receiving end of a high hit from Blues forward Oskar Sundqvist. He had been listed as day-to-day while in concussion protocol.
In 19 games this post-season, the 25-year-old has three goals and seven points.
Sundqvist was given a one-game suspension for the hit from the league’s department of player safety.