I think injuries are definitely catching up. Whether that is the primary reason for the poor game the other night, I don't know.
But when you look at the official injuries list, out of the 8 teams left, it isn't even close which team is suffering the most:
http://www.tsn.ca/nhl/injuries
And those are only the official injuries. Hudler and Monahan are likely playing well below 100% right now. I also suspect that Ferland, Russell and Wideman are playing with some kind of injury.