The full-back's starting position

Watch the first ten minutes of any match and ignore the ball for a moment. Look at where the full-backs stand when their team has possession.

Against Milan last season, Empoli kept both full-backs narrow, almost touching the centre-backs. That compressed the middle and forced Milan's wingers wide. But it left the entire flank open behind them. Leao didn't need to beat his man. He just ran into the space the full-back had abandoned.

A full-back who stays narrow is protecting the centre at the cost of the wide channel. The moment possession turns over, that space becomes a highway for the opposition winger.

Watch the first few minutes to see if the full-back is covering the flank or squeezing inside.

Question: Who is the full-back covering when the opposition winger drifts inside?