RB Leipzig had 4 players in their defense line against Borussia Dortmund. And Leipzig used their full backs so aggressively when they met Borussia Dortmund (like they usually do). But with 4 defenders, the problem is, there are 4 players in each central spaces (for 2 half-spaces, 2 players and if we divide centre to 2 spaces, in direct direction according to a 10 metres length, 2 players for centre). And what it means is, when you want to use your full backs aggressively and send them to press also wings, when one full back shifts to a wing and other defenders shift too, 1 of these 4 central spaces will be free for opponent. And if you want to cover all central spaces, this time distances between defenders will be too much so forward players can move easier and also escape to defenders’ behind like Borussia Dortmund did against RB Leipzig (this is how they scored the first goal, the one cancelled, and then how they won penalty).