I’m not sure there’s a right or wrong really, positives and negatives to both ways, but I guess the theory is that creates more space in the penalty area for attackers to make runs and get free for a clear header. If you pack the box with more players, you maybe reduce your chances of winning the first header, but also make it much harder for the attacking team to get a clean contact and route to goal.
I think leaving one up is a pointless token gesture, but leaving two or more up gets interesting and makes the opposition think about what they’re going to do in response.
I think that leaving someone like Cal Roberts forward is a good idea, not just as an attacking threat but equally as a first line of defence. The problem with leaving nobody up is that when the ball gets cleared, their player has time to look up and pick a pass which is usually straight back into our penalty box. If someone is there to harry them, it's more likely to lead to a sideways or backwards pass.
Nah, you want Roberts on the edge of our box to try and run onto a headed clearance for me. He’s effective when he has the ball and is running at players. If you leave him up, he’s not quick enough to reach a ball in behind, or likely to be strong enough to get hold of a long clearance. Pressuring a second ball back in is one thing a player up can do, but it’s all about what you see as most important I guess.