Attacking is all about vision, seeing what is in front of you, identifying space, and playing into it. So, on defence, you want to sell a solid picture where the attacker cannot identify any weak spots, and at the same time minimize the attacker's decision making time. The outside shoulder principle can add another dimension to your defence: blind spot tackling. With the pressure of minimized decision making time, the attacker will now also feel the pressure of not being able to accurately track the coming defender. He will know the defender is coming but he will not be sure of where he is. The outside shoulder principle requires the primary defender to lineup on the receiver's outside shoulder. This means it is a 50 - 60 cm difference in setup. Where a defender would normally be frontal, or on the inside shoulder, he now sets up a step wider to line up with the outside shoulder of the receiver.
This enables the defender to set up just outside the peripheral vision of the receiver. The receiver then struggles to keep track of the defender. Keep in mind, the receiver may scan what is ahead but for that last second or 2 he must keep his eyes on the ball. While doing so he can still see most of what is in his peripheral vision, but it will be very hard to keep track of the defender coming from just outside of it. For most teams, the inside defender is the jackal. A good blind spot hit will not only cause an attacker to fall awkwardly and struggle with placing the ball back on the ground, this will all be happening right in front of the jackal. You are manipulating the carrier to run to your jackal. You just have to make the hit, to set up your jackal to do what he does best.
Keep the following in mind:
This is not a system, it is a principle.
50 - 60 cm in setup is all that is needed.
It can be used in any system.
You can, but don't have to do it all the time.
A good understanding of this will result in players naturally executing it with great timing and in the ideal situation.
Consider applying it in specifc zones and/or specific channels
Just like attack, defence is all about outsmarting the opponent.
I hope this sparks some thinking for you!