The Eagles had won their last four matches coming into the match, including nine of their last 10 as they went into the game as red hot favourites.
However, the Bulldogs proved far too good, as their relentless pressure and pacey counter-attack tore the home side apart, who were forced into a plethora of uncharacteristic errors.
Simpson said post match that the loss was tough to deal with.
“Every time you lose a game like this in a final you feel like you’ve wasted the whole year,” Simpson said.
“We probably regressed back to relying on too few. And you look at the Doggies and what they did, it was a collective group and ours wasn’t.
“That’s our ambition and what we’re trying to do but tonight we didn’t do it. Unless everyone is firing you’re going to struggle in games like this.”
West Coast finished the home and away season in sixth place with 16 wins and six losses, and won just half a game less than last season, when they finished second on the ladder.
The Bulldogs will face the loser of tonight’s qualifying final between Geelong and Hawthorn at the MCG in the semifinal next weekend.