A heroic performance from Matt Reis was not enough to deny Sporting, which advanced to its second conference final in three years.
Playing at home and trailing a goal on aggregate, it was no surprise that favored Kansas City grabbed the initiative in the first half. New England's veteran Keeper Matt Reis was impressive in the face of pressure, commanding his area and coming up with a number of stops, the most impressive a reflexive dive to deny Dom Dwyer's header from close range.
Kansas City eventually made the breakthrough a few minutes before halftime. Chance Myers' cross fell in the New England penalty area and was misplayed by defender Andrew Farrell, allowing Sporting's Aurelien Collin to tuck inside and stab home the goal.
New England refused to lay down and accept defeat. Reis came up with a big double stop in the 56th minute to deny Dwyer and Benny Feilhaber, and in the 70th, New England struck to level the game and retake the aggregate lead.
It was Dimitry Imbongo who put an acrobatic scissor volley on the end of Kelyn Rowe's swinging free kick, but Sporting goalkeeper Jimmy Nielsen will be upset to have bobbled the ball into his net despite decent positioning.
The lead lasted less than 10 minutes. Sporting left back Seth Sinovic, a former Revolution draft pick who was later released by the club, notched an emphatic strike in the 79th minute, coming in behind the Revs defense to slam home a first-time strike off Graham Zusi's flicked header and restore parity.
It took untl the second half of extra time to finally separate the two sides. Former Rev Feilhaber intercepted a Reis throw in New England's half, came down the right wing and threaded a low cross to the unmarked Claudio Bieler, whose first-time shot beat Reis and sent Sporting Park into raptures.
New England's situation only worsened from then on, as Reis had to be helped off the field late in stoppage time, forcing Farrell in between the sticks for the final, desperate moments of the game.
Sporting will travel to Houston on Nov. 9 for the first leg of the Eastern Conference finals.