Matt Grzelcyk remains in concussion protocol and will miss his second straight game for the Boston Bruins against the St. Louis Blues in Game 4 of the Stanley Cup Final at Enterprise Center on Monday (8 p.m. ET; NBC, CBC, SN, TVAS).

But Bruins coach Bruce Cassidy said the defenseman is improving and there is a possibility he could return later in the best-of-7 series, which the Bruins lead 2-1.

"We'll get back to Boston, see where [Grzelcyk] is at," Cassidy said Monday. "He's better than where he was, so there's a chance for him."

Grzelcyk was injured on a hit from Blues center Oskar Sundqvist in the first period of Game 2 on Wednesday. Sundqvist received a boarding penalty on the play and was suspended for one game by the NHL Department of Player Safety.