The Rapids needed a significant turnaround after losing the first leg by the same scoreline last Sunday but it was Kansas City, roared on by their home crowd, who performed with the urgency to advance to the conference final with a dominant 4-0 aggregate win.
"Zusi has an amazing foot, every time he (serves) we feel we can score," Collin told reporters. "We did an amazing job today. It was not easy to play against this team in this weather. I'm very proud of my team tonight"
Kansas City played aggressively despite the drizzling rain and forward Sapong set up the first goal with a charging run that resulted in a foul in the 27th minute.
Aiming to become the first back-to-back MLS Cup Champion since the Houston Dynamo in 2006-2007, Colorado were uninspired in defeat.
They were also weakened by injuries to forward Caleb Folan and Kosuke Kimura in the first leg, adding to a casualty list already featuring midfielder Jamie Smith.
Sporting will face the winner of the other semi-final between Houston Dynamo and Philadelphia Union for a place in the MLS Cup final. Houston lead that tie 2-1 after the first leg.
(Writing by Jahmal Corner in Los Angeles, editing by Nick Mulvenney)