German referee Felix Zwayer went down with cramp on his World Cup debut on Friday and needed a shot of magnesium to finish the US's 2-0 win over Australia.
The heat in North America has led to widespread fears about player health but the impact on referees - who generally run as much anyone in a match - is less discussed.
Fourth official Katia Garcia came to Zwayer's aid with the magnesium drink late on in Seattle. The 45-year-old is the only German referee at the tournament and German TV refereeing pundit Patrick Ittrich told Magenta: "An outstanding performance."
Ittrich hopes his friend will be fit for other World Cup games.
