The goalkeeper’s first job is to stop shots, but modern goalkeepers also act as an extra defender in build-up, playing out of the back and sweeping behind a high line.
Good goalkeepers combine shot-stopping with command of the area on crosses and set pieces, quick distribution with feet and hands, and communication that organises the back line.
In a 4-3-3 or 3-5-2, the GK often starts the first phase of build-up, splitting the centre-backs and drawing opposing strikers into an initial press.