Wrensted started his career with Geradlton Railways before being recruited by West Australian Football League club East Fremantle (whose country zone he was in) for the first six matches of 1983.
He was successful enough that the newly christened "Sharks" signed Wrensted to a permanent contract after five matches.
[1] Wrensted improved steadily and had his best season in 1985, winning a Sandover Medal with a record tally of votes and ending the year by playing in a premiership side.
A centreman, Wrensted joined West Coast in 1987 for their inaugural VFL season.
In 1988 the club made the finals for the first time and in the Elimination Final against Melbourne Wrensted had a chance to win the game with just seconds remaining but his shot from 40 metres out on the run drifted wide and they lost by two points.