We rehearse full backs running outside wingers and almost never rehearse a midfielder running beyond a striker who has come short.
Nobody trains the overlap that goes past the centre forward
A striker drops in between the lines. The centre back follows him for three or four metres, then stops, because following any further means leaving a hole where he is supposed to be standing. The hole is now open and there is nobody in it. That is the most common wasted moment in professional football and it happens twice a half.
Everyone calls it a third man run when it works. Fewer teams train it, and the reason is that it belongs to nobody. Full back overlaps have an owner: the full back. Wide combinations have owners. But the run past a dropping striker has to come from a central midfielder who is also responsible for rest defence, or from a winger who has been told all week to hold width and stay chalk on his boots. Both have a standing instruction that says do not do this. So they do not.
The teams that get it right make it explicit rather than hopeful. If the nine comes short, the far winger goes, no discussion, and the near winger becomes the width. That is a rule, not a read, and rules are what you need when the window is a second and a half.
I would push it further than most coaches are comfortable with. The run should be made when the pass is not on. If your midfielder only goes when he can already see the ball arriving, the centre back sees the same picture and drops, and nothing opens. The value is in the run that empties the space for the striker to turn into, and that run has to be blind and it has to be wrong most of the time.
The objection is fitness and I take it seriously. You are asking a central midfielder to sprint sixty metres knowing four times in five he will jog back. That is a real cost against a side that turns the ball over well.
Here is my complaint about how we discuss this. We talk endlessly about the full back overlap because it is on the wing where the camera lives and it ends in a cross that gets counted. The run past the striker ends in a defender's hesitation. Nothing counts hesitation, and hesitation is what wins games.

