After the Bruins 4-2 win in game three, head coach Jim Montgomery shared an update on Krejci's status and whether he'll be available for game four, as per Fluto Shinzawa of The Athletic:
Good chance that Krejci is still ailing from the nagging injury that kept him out of several games down the stretch in the regular season. Like captain Patrice Bergeron, Krejci will - obviously - be most valuable when healthy.