To many passengers and slow guys
Don't know about "passengers" but there definitely are too many slow guys who not only can't skate fast but also can't make a quick enough hockey decision in the moment before opponents can anticipate what they're about to do. All you need to have is one player on a line who isn't getting his job done and it throws off the whole line. Take the 1st line principally, I think Iginla has been lucky to get a couple of goals deflected off of him and also just being in the right place for a deflection or two (which is a positive in and of itself), but for the most part he's been slow on the puck. The same goes for Lucic; skating around like a freight train when he's got a spur under his saddle, but no great speed and not a whole lot of knack with the puck. Put Krejci with them, and the whole line being pressured, and the next thing you have is Krejci holding on to the puck too long, the losing the puck, and also himself being snake-bitten when he has scoring chances, and the end result is a line which is less than a shadow of itself from the Regular Season.
Then add to that Marchand who's skating around most of the time with his head up his ass. I mean, I like Marchand and I wish he'd get his act together, but he's really not offering anything positive to the team right now.
And lastly there's Chara, who shouldn't really be criticized extremely for his age, because still he's one of the best Dmen in the League, but against a speedy team like Montreal he's not always the elite performer that he used to be. He was never the quickest skater around to begin with.