Defending MLS Cup champions Colorado Rapids have been knocked out of this season's play-offs by Sporting Kansas City on Wednesday.

Kansas City led 2-0 after the first leg and a goal in each half at Livestrong Sporting Park from Aurelin Collin and CJ Sapong gave the hosts another 2-0 success.

The 4-0 aggregate victory sets up an Eastern Conference final against either Houston Dynamo or Philadelphia Union for Peter Vermes' team.

Real Salt Lake preserved their first-leg advantage to move into the Western Conference final at the expense of the Seattle Sounders.

However, Osvaldo Alonso's 56th minute penalty and substitute Lamar Neagle's goal five minutes later made for a nervous half an hour before Salt Lake progressed 3-2 on aggregate, setting up a final against either Los Angeles Galaxy or New York Red Bulls.