From phase to phase, defenders not involved in the tackle or tackle contest need to re-build their defensive line as quickly as possible. Players must plug gaps and establish width, ensuring that the area around the breakdown is secured first. Teams in possession of the ball can build momentum if they can gain ground quickly after a tackle, and this would be the shortest route.
When defending fringes of the breakdown some teams employ two players, others four, but three defenders provide a solid wall that covers the basic necessities. For the purposes of this explanation, they will be labelled the A, B, and C defenders.
What are the actual responsibilities of these players? In the diagram, you can see how they are stacked up and aligned relatively flat with one another, thus preventing any obvious gaps to attack and ensuring the line has a better chance of advancing together.
A Defender – has the responsibility of the gap closest to the tackle contest and should be close enough to touch it. Once players have established themselves here and even if there is time for players to get into ‘better’ positions (i.e. forwards closer, backs wider), this person never leaves that gap until the ball is long gone. If he/she leaves, a clever scrum half or forward could snipe into that space and make the entire line retreat and re-organise. This role is about protection but it’s also about pressure. When the ball comes out, the A on BOTH SIDES must pressure the passer or picker. If caught, this is a great opportunity to steal the ball as the attacking team’s support has to come back while the defensive team should already be moving forward together as a unit. If an attacker decides to run into this well-guarded space, a tackle behind the previous ruck has a very low chance of being won back.
B Defender – has a very similar role to A, staying tight to the breakdown. In some countries, this defender is referred to as the ‘body guard’ for good reason. If only A occupied the space between the tackle contest and the first receiver, one could easily direct two forwards into that gap to either hammer or offload to get through. The B, then must work together with A and C to form a solid wall of pressure between the passer and the first receiver (often the fly half). B must guard against a scrum half’s arcing run, a player coming around from the blind side or an inside ball from the first receiver.
C Defender – has the easier-to-explain role of marking the first receiver, who is most often the fly half. If this player is a big forward who has some doubt about covering an elusive back, and there is time to do so, C can swap with B. The player moving in toward the ruck should be the one who goes in front, with the player moving out going behind. Again, the fringes of the ruck are an appetising spot to attack if not defended properly, so it’s important that the interior players be fully aware.