In October 1986, Worsfold was named as a member of the West Coast Eagles' inaugural 32-man squad. He made his senior debut for the club in round four of the 1987 season, against at Princes Park. Worsfold played a total of 11 games in the club's inaugural season and also played five games in the WAFL for South Fremantle. The following season, he cemented his role in the side playing every game except for two games missed due to suspension in rounds nine and ten. At the end of the season, Worsfold was awarded the Club Champion Award as West Coast's best and fairest, winning by ten votes from runner-up Guy McKenna. He was also awarded a total of five votes in the Brownlow Medal for the best player in the competition, including two votes for 30-disposal and 28-disposal games against and . Worsfold played in his first finals match at the conclusion of the 1988 season, a two-point loss to at Waverley Park. Worsfold led West Coast in disposals, kicks, and tackles in 1988.