Krug scored 32 points in 63 games last season which is respectable for any defenseman. While he has not been the same as he was with the Bruins, he is still one of the Blues best defensemen and could still bounce back for a Norris-level campaign.
Krug has suffered many lower body injuries in the past but it is not known how many of which were to his foot. If this injury is reoccurring, this has the potential to keep him out of play for months but if this a first-time thing handled with care, Krug could potentially return a few games into the season.