Wetherall was born in Sheffield. He was capped by England at schoolboy level, and in 1989, when he left school, he signed for Sheffield Wednesday under the management of Howard Wilkinson. Wetherall had attended Rotherham sixth form college where he achieved four A-levels at grade A, and chose to study for his BSc in chemistry at the University of Sheffield, so that he could live at home with his parents and combine his education with playing for Sheffield Wednesday's reserve team. He graduated with a first-class honours degree in 1992, becoming the first Premier League player to achieve such a qualification. In 1990, he was part of a British squad which travelled to Italy for the world student five-a-side football championship, and represented Great Britain as they won the association football bronze medal at the 1991 World Student Games hosted in Sheffield.