Fast was diagnosed with a sprained knee after leaving Saturday's game against the Predators, Andrew Gross of the Bergen Record reports. Coach Alain Vigneault went ahead and ruled Fast out for Sunday's game against the Stars, but the forward's status beyond that should be known within the next couple of days. Predators goalie Pekka Rinne recently suffered a knee sprain and missed three weeks, so Fast could be looking at a similar multi-week recovery timetable.