Remember that old children's verse: "for want of a nail?" It goes, "For want of a nail the shoe was lost. For want of a shoe the horse was lost.
For want of a horse the rider was lost. For want of a rider the battle was lost. For want of a battle the kingdom was lost. And all for the want of a horseshoe nail."
In the case of the Habs, Andrei Markov is the nail and the playoffs are the kingdom. What it comes down to is the Montreal Canadiens really need a defenceman. Nothing against Alexandre Picard; despite his occasional brain farts, he's acquitted himself decently as a number-six D so far this season. The problem is, the Habs don't need a number-six. They need a number-one. Or, at the very least, a top-four guy.
The consequences of Andrei Markov's absence run much deeper than just missing the man himself, which is hard enough. Without him, P.K.Subban is making his rookie mistakes while paired with a just-competent journeyman. Subban needs an on-ice mentor who can teach him and cover for his errors, which currently end up in the Habs net way too often. Without Markov, his learning curve is much, much steeper.
Without Markov, Hamrlik and Spacek become the top defensive pair. Unfortunately, they're not as young as they used to be, so their minutes need to be managed. If they're to play smaller minutes than the horses who lead other teams on the blue line, somebody else has got to step up. That means Gorges and Gill play more than they should, including at times when the team is trying to score...which is definitely not their forte. In fact, scoring is not the specialty of any of the blue line corps.
Without Markov, the Canadiens have only one way to win. They take an early lead, then patiently defend it while they wait for an opportunity to build on it. This method depends on actually getting that early lead while the other team is still getting a feel for the game. It also depends on Carey Price playing otherworldly-good hockey, rather than just ordinary good. For most of this year, the plan has worked pretty well. Lately, though, Price is coming back down to earth and playing only well rather than superbly well. Fluke goals and softies that didn't figure into the plan earlier in the season are causing problems now because without Markov, the Habs can't score very much.
If the plan breaks down and the opponent scores first or manages to pull ahead later in the game, the Canadiens don't come back. The forwards have to start their rushes at their own blueline and battle through to the offensive zone because they have no help from their defence. When they do get to the o-zone, the forwards don't go to the net as often as they should, so they end up passing around the perimeter instead of getting chances on net. They have no threat from the blueline who can break the cycle with a hard, accurate shot. The opponent can just collapse around their goalie and keep the Habs to the outside, which they usually do pretty effectively.
The Canadiens have learned a method of winning without Markov, but it's precarious and depends on everything going according to plan. The Habs are not a team that will blow an opponent out of the water very often. They rely on hard work, discipline and opportunism. When something goes wrong, they find it very, very difficult to recover. This is a deep, systemic problem and the only cure is to bolster the defence with a guy who can pass the puck and who's a threat to shoot from the blue line, while also playing a steady game in his own end.
There aren't a whole lot of candidates out there who might also be available to sign or trade for. Kim Johnsson is without a team, but he's dealing with post-concussion syndrome and may not even play at all this year. Tomas Kaberle comes to mind, but dealing with the leafs and probably giving up a first-round pick to them is repulsive. Still, it may happen that the Habs don't have a choice. The only goal they should have right now is staying ahead of the Bruins. Doing that much will ensure a playoff spot. They're now in danger of falling behind, and, if they do, they'll shortly be at risk of falling out of the post-season picture as well. Ideally, Gauthier would wait until the trading deadline to make a move. In reality, the Canadiens may not be able to hold on that long.
For want of a nail...or a Markov...the season could be lost.