Looking for a drill for my HS team

I'm coaching a JV high school inline team, and the kids are doing well. But, we only have a couple with a lot of competitive experience.

One of the things to which we've been susceptible is back door plays. Our defense, especially the younger guys, get into "chase the puck" mode, and the leave the back door open.

Anyone have any drills for practices to work specifically on back-door defense? I haven't been able to find any and I'm not creative enough to create any that would work.

Anyone have any ideas?

one idea for games- run your defense as a half zone, so you leave each of your two defenseman responsible for one side of the net and the forwards can chase.

Small area drill: Playing the width of the rink, put two nets back-to-back in the center of one offensive zone like this: ][

There are tons of variations you can dream up here, but one that would be particularly good for back door plays would be to put out two defensemen and two forwards; only the forwards try to score, and they can use either net.

This forces the defense to play very tight since it's quite easy to reverse the play and score on the other net if the coverage is poor.

If you'd like to throw a bit of a fun competitive twist into it, my teams used to give the forwards a time limit to score - if they scored within that limit, the D would run a sprint to the opposite end (and vice versa if the D held).

One drill I used to do at Harvard was putting the net in the corner, facing the corner, and make it a 2 on 2 situation. Since it's very hard to score from in close on a shot like that, the offense usually goes for the back door score. Make it even more interesting by making both teams able to score. You quickly have to transition yourself from offense to defense if the other pair gets the puck.

Start the pairs on opposite sides of the net, dump the puck in and make them both go after it. That really helps with teaching guys how to win pucks along the boards, as well as staying on the D side of the man in a defensive situation. If a shot goes wide, dump another puck in. We call the game "puck goes in the net" because that's when the drill ends. Also great for your goalie to get work in on quick, close shots and finding a puck in traffic.

Alternatively, we do a drill where players start in pairs in the corner. One D follows one F to the high ("offsides") dot, where they turn around and crash the net. A coach or another player at the low faceoff dot feeds a pass to the front of the net (make it a good, hard one). The offensive player is trying to get open or at least get a stick on it. The D is trying to stay with their man and tie them up as they go to the net. The F ideally should be going to the far post to look for the back door play, so emphasize that, but at the same time, let them be creative and learn why that is the best option. Enforce that this is not a 2 on 1 situation, but a 1 on 1 without a puck. Work with your defensemen on knowing how to both look for the puck as well as knowing where their man is and staying on him.
This also is a very good drill for forwards to work on playing defense, since often times it is a high guy cutting hard to the net rather than a forward, and many forwards do a terrible job of getting body and stick position on the guy that they are covering.
One other major point of emphasis on this is keeping your D between their guy and the net. Wayyyyyy too often now in roller hockey, especially teams that play man to man, the D is simply following the F around the rink (I call it Linus and Sally, which obviously these kids don't get). As soon as the forward comes around and has some space, they take off, and the D is left standing there while a guy cuts down the middle wide open. Teach them now to stay between their guy and the net. Not doing that also is the reason for probably 70% of hooking calls. This is a great drill to teach and emphasize that.

Thanks, all. Really appreciate the help. In games, we mostly play straight zone. Most of our kids just can't keep up with their competition in man-for-man. I'm going to try a couple of these. I especially like the back-to-back net idea, and the 'crash' drill.