Claude Julien is famous for his demands in terms of defensive play. He establishes a tight system in his team's zone, wants forwards to be responsible, and asks for a lot of positional awareness from his players, especially the centres. The elements that made him successful with the Boston Bruins — ones that earned him a Stanley Cup and another Final appearance — are now being tentatively implemented in Montreal.

There's a difference between using a system on a team you have been coaching for years, with players that are very much used to this style of play, and using this same strategy on this year's Montreal Canadiens squad; a group comprised of a lot of new faces that come from diverse organizations, and are not always used to this specific approach.

Since the beginning of the season, there have been more than a few defensive errors. Most were related to defending against rushing attackers, but the confusion in the defensive zone is also apparent.

With your number-one centre having just switched to the position, a rookie defender on the top pairing, and Karl Alzner coming from a Washington Capitals team that uses man-on-man coverage, the transition to a system that relies on rigid zone assignments has been difficult.

It's hard to pinpoint a team's standard defensive system on the ice. NHL hockey is incredibly fluid, and there are not many opportunities in a game to freeze-frame a play and compare it to the drawings in Julien's office. Here's my best attempt at it:

What is Claude Julien's system?

When the puck is behind the net, one of the defencemen has to flush out the opposing forwards. That means applying pressure from one side of the ice to have the attackers commit to the other side. The second defenceman then takes over and jumps on the puck.

Below the goal line, the defensive formation usually collapses on the opposition with both defenders and the F1 (the centre most of the time). The winger on same side of the puck (F2) remains higher in the zone and close to the boards to try to cut a pass back to the blue line. The other winger (F3) prevents a cross-ice play, but also has the responsibility to cover a back-door attempt by an out-of-sight defender crashing the net.

In the half-wall battle, the defenceman responsible for that side of the ice is directly pressuring the puck-carrier, F1 is supporting, and F3 is in the same position as before. The other defenceman is covering the front of the net.

F2 is usually closer to the puck battle in this situation, in order to constantly outnumber the opposing forwards on the boards and give the team a better chance to win possession. He also prevents a direct access to the slot and still has the responsibility to intercept a pass going to the blue line.

In motion, this is what it looks like:

Shea Weber pushes the Los Angeles Kings forwards to Victor Mete’s side of the ice and then joins him on the back wall along with F1, Alex Galchenyuk in this case. As the play transitions on the half-wall, Weber backs off to cover the front of the net, and Max Pacioretty (F2) joins the pressure. The puck is won and it allows for a quick transition the other way.

Comparing with Michel Therrien's system

There's not much difference between Julien's and Therrien's defensive system low in the zone. They both seem to use this 2-3 formation, corresponding to the half-wall setup. This is a pretty classic strategy across the NHL.

Clip from a 2016 game against the Bruins.

The two coaches only vary in choosing how much they collapse on the puck down low (with Julien seemingly using a more aggressive approach) and how they pressure the other team's blue-liners in the defensive zone.

Under Therrien, forwards routinely skated to opposing defencemen to try and force turnovers by blocking passes or deflecting shots with their sticks.

Clips from Therrien's Habs

The new Habs coach prefers to protect the slot at all costs and doesn't mind allowing shots from low-danger areas. It is apparent in how the wingers conduct themselves in the defensive zone in both his tenure with the Bruins and now with Montreal.

This season, when the opposing defencemen have full control of the puck and passing options at the blue line, they receive little pressure from F2 and F3. Instead, the forwards usually try to block the shot from further away or choose to let their goaltender handle it. At times, they even form a kind of box in between the dots to achieve this.

In theory, this should mean that the Habs players outnumber the opposition in the slot and are able to clear rebounds easier, and limiting high-danger scoring chances.

However, it also gives the other team's forwards an easy relief from pressure when they are low in the zone. They can get the puck to their defencemen at the blue line for a shot on net or a quick transition of possession to the less-crowded side of the ice.

Zone vs. Man-to-Man defence

The player who had to change his game the most this season — after Jonathan Drouin — is probably Karl Alzner. Coming from the Washington Capitals, he needed to unlearn his man-to-man coverage tendencies to fit in the zone-defence system that Julien uses.

That means that instead of chasing the same guy in the defensive zone, sticking to him until he gets too close to the blue line (at that point becoming the responsibility of one of the forwards), he has to cover a delimited area of the ice and generally play within it.

In this sequence, Brooks Orpik, a Washington defenceman, is covering Crosby along the boards and follows him until he is dragged too high in the zone. Ovechkin slides back to let his defencemen attack the puck-carrier. Orpik gets on #87 again when he skates below the dots, and hinders him from making a dangerous pass to a teammate.

Meanwhile, in a similar position, Mete chooses to let his winger handle the forward with the puck after a short pursuit along the boards. He retreats to his assigned space in front of the net, instead of chasing him above the faceoff circles.

This is the main difference between man-to-man and zone defence. There are a lot more switches in coverage in the second strategy, meaning that as opposing players move in the defensive zone they becomes the responsibility of different teammates at different times. It can take a while to get used to when you transition from one system to the other, like Alzner is currently doing.

Zone defence demands

The issue with zone defence, and what we see on the ice sometimes with the Habs who are partly inexperienced with this, is that players aren't always sure of which player they should be defending in their own zone. When not executed properly, zone defence can lead to extended offensive zone possession for the other team, or goals against with more glaring breakdowns.

On the play in the following clip, Mete first hesitates to jump on the puck-carrier after Weber flushes him to his side. That creates time and space for this opposing forward to find a one-timer option in the slot. Then as the play switches back to the left of Montoya, Tyler Toffoli is abandoned in front of the goalie as Habs players are unsure of their assignments and caught puck-watching.

Being a tad late on your coverage can lead to playing catch up for a while in the defensive zone. It's important that every player understands their duties, otherwise it becomes easy for opposing forwards to sneak through as, once again, defenders don't have a specific player to watch for at all time.

Still, zone defence doesn't only mean patrolling a specific part of the ice, you have to stay with your coverage in your designated space. For the centreman (F1) that usually means staying lower in the zone and closer to your defencemen.

The clip below is San Jose's first goal of the game last week. Drouin fails to recognize the three-on-two that is happening below the dots as Logan Couture is circling back to the net. Morrow also lost track of the play, taking himself out by cross-checking a forward that didn't have the puck, instead of being in position to protect the access to the slot.

This play cost the Habs a goal very early in the game, and could have been easily prevented. The system forgives small lapses in coverage as opposing players usually have to go through multiple layers of defence to get to the net. But when both the centreman and the defender on the same side of the play lose track of the puck, then your goalie becomes your only hope.

Conclusion

There are a lot of advantages to a zone-defence system, and if executed well it can work wonders. With how much pressure the other team faces below the dots, it all but takes away their ability to cycle the puck, and make plays on the side of the ice they are currently on. It becomes a lot harder for them to get access to the slot and create high-percentage scoring chances. Overall, it can really suffocate the other team's offence leaving them with only a few less-threatening options.

Right now, the Canadiens’ issues don't stem from the system itself, but how they play in it. For most players, Julien's strategies are not that different from what they were used to under Therrien, and those differences are not enough to create the chaos we have sometimes seen on the ice.

In theory, the system is a perfect design for a team that has one of the best goalies in the world. But the execution will have to be better, including from Carey Price, if the team ever wishes to get out of the hole they are digging themselves.