In this edition, Corsi, the former goaltending coach of the Buffalo Sabres and St. Louis Blues, looks at how the modern-day defenseman is changing how teams attack in the offensive zone.

The Coaches Room is a weekly column by one of four former NHL coaches and assistants who will turn their critical gaze to the game and explain it through the lens of a teacher. Jim Corsi, David Marcoux, Paul MacLean and Joe Mullen will take turns providing insight.

In my first column, I wrote about how 5-on-5 scoring is on the rise because of net accessibility, which is a result of unscripted offensive zone play and in many ways the new script in the NHL.

Taking a page out of that script, I was recently talking with Montreal Canadiens associate coach Kirk Muller about 5-on-5 scoring. I asked Muller if he agrees with me on the three ways teams have found a way to attack collapsing defenses, because every defense in the NHL now is a collapsing defense with a shot-blocking mentality.

He did.

We have such a collapse in the defensive zone by the defensive team. It's a protect-the-net mentality. Clogged up shooting lanes have long been a topic of conversation. How do you get the puck through? Where do you shoot? How can a team generate offense?

There is a growing trend in the League to activate the defensemen, making them more of a free radical on the ice to be part of the attack, and to change the strategy for the third forward. By doing this, teams are creating opportunities to set up chances. The rest is unscripted.

Here is what I have been seeing:

1. Third forward at top of circle

We often see two-man battles for puck control in the corner. The third forward used to always shade toward the slot. Now we're seeing him shade out to the top of the circle.

The idea is for the other two forwards to gain possession in the corner and then look for the third forward at the top of the circle. A lot of the time he's open. The defender in front of the net isn't sure if he should cover him because he's too far away from the net. The strongside defensive winger is in the scrum in the corner with the center and the weakside winger is shading toward the slot, because the weakside attacking defenseman is a threat.

So, this third forward is in no-man's land, and he's a trigger man. He'll get the shot off and both guys who were in the corner are now going to the net. At the same time, the third forward is the safety valve if his weakside defensemen wants to creep down the side to look for rebounds.

The defenseman can creep down because he has offensive instincts, which we see in a lot of modern-day defensemen. More on that later.

2. Stretching out the team's collapse

To counter against the collapse, coaches are telling the third forward to move even higher, in between the two defensemen, who spread apart to make room for him. Now there are three guys high, so a defensive player has to come out and cover that high forward.

By expanding the collapse by inviting players to come out and cover them, more room is created in the slot.

What happens next is the offensive team may get off a shot from the top of the zone by the high forward, or one of the defensemen can drive down the boards and throw a puck toward the net to look for a deflection and rebound opportunities for the two forwards in front.

Just like in the first example, the third forward is high enough to act as a safety valve against a counter that may come with the defenseman lower in the zone. The third forward also can drive toward the net, following almost parallel to the defensemen bringing it down the wall.

3. Using the area behind the net

This last one is something that was perfected years ago by Wayne Gretzky.

Strongside defenders will swarm toward the puck in the corner or along the wall and weakside defenders will turn in that direction. As the puck moves up or down the wall, the swarm follows it. But one of the attacking forwards will linger behind the net.

If the attacking team gains possession, they'll try to pump it around to the forward behind the net. This forces the goalie and the defenders to turn and look behind them, leaving them vulnerable to the other attacking forwards or defensemen slashing toward the net.

As coaches we tell guys the age-old line, "head on a swivel," but human nature has the goalie and defensing team looking at the puck.

So what happens is the puck gets driven behind the net and the defense has to figure out who is going to attack the forward, but while that is happening, the other two forwards are going toward the net and one of the defenseman is coming down the wall.

What I'm trying to get across here is despite the fact that everybody is blocking shots, teams are figuring out how to stretch out the collapse so they can generate the shot and allow their guys to hunt down rebounds.

We have defensemen who are more active like Erik Karlsson of the Ottawa Senators, P.K. Subban of the Nashville Predators and Duncan Keith of the Chicago Blackhawks, whereas years ago defensemen who could fly, Brian Campbell for example, would take the puck and skate with it.

Now, instead of being active members only on the rush, these defensemen are active members of the offensive zone attack.