Many players cramp late in matches, especially in extra time or heat. The traditional explanation is dehydration and salt loss, but the picture is more complicated.
Two main theories exist: fluid and electrolyte loss, and altered neuromuscular control due to muscle fatigue
Cramps often occur in fatigued muscles, even when players are not severely dehydrated
Heavy, salty sweaters in hot conditions may still benefit from extra sodium
Stretching the cramping muscle usually relieves it in the moment
Practical steps that tend to make sense: build match fitness so players are less fatigued late on, plan drinks and some sodium in hot conditions, and look at recent load. Cramps often appear when players are suddenly asked to play longer than they are used to, for example after an injury layoff.