Standing alone in the 18-yard-box, they're vulnerable, relying on their rearguard to help him protect the goal.
More after the break
Exposed to the vitriol spitting from the stands, the goalkeeper has no escape from criticism.
They can be redundant for 90 minutes and then be called upon at the death - the difference between winning and losing.
It's a position that requires steely mental toughness. During his 13 year career, former England goalkeeper Paul Robinson has built the mental resolve to deal with the highs and lows of the number one role.
In this video he shares his psychological techniques for staying focused on the game.
Paul Robinson is an Under Armour-sponsored athlete: for information, visit underarmour.co.uk
Paul Robinson: Nutrition for goalkeepers
Winning a one-on-one: a 3-step guide
Paul Robinson's essential goalkeeper drills
Paul Robinson's guide to saving penalties
In the gym with Paul Robinson
Summer fitness plan for goalkeepers
Paul Robinson: Summer fitness
Paul Robinson: Prepare for pre-season