The 21-year-old Victorian, who played for Gippsland Power in the TAC Cup, could only manage 11 games in three seasons with John Worsfold's side, unable to break into a team already boasting a number of inside midfielders.
Stevens, who was taken with pick 23 in the 2009 national draft, played in a losing WAFL grand final for East Fremantle on Sunday and West Coast list manager Craig Vozzo said the club were disappointed to see him go.
"Unfortunately, Koby has informed us that he would be seeking to be traded to another club in pursuit of further opportunities," Vozzo said.
"That's extremely disappointing because we saw him as an important player in a developing midfield.
"Koby is a young player with some terrific attributes and we had hoped he would remain with our club to be a part of what we believe we are building towards. Having said that, we understand and respect Koby's decision, and will work to ensure a suitable outcome for all parties."The Eagles also delisted injury-plagued small forward Ryan Neates, who made his debut in 2012 but could only manage that solitary appearance, as well as rookies Michael Mascoulis, Anton Hamp and Callum Papertalk.