Chelsea’s defensive crisis: Alonso’s system, missing pieces, or individual errors?

In Alonso’s system, the player at the base of midfield is one of the central components of the team’s ‘Rest Defence’ — the structure left behind the ball while Chelsea attack.

A center-back may appear responsible for allowing an attacker into the penalty area, but the tactical breakdown may have occurred several seconds earlier when Chelsea’s first and second defensive lines became disconnected.

Wing-back attacks ↓ Chelsea loses possession ↓ Midfielder fails to stop counter ↓ The center-back must defend wider area ↓ Defender mistimes challenge ↓ Goal: Who is responsible?