Christian Ramirez and Cucho Hernandez scored extra-time goals as the Columbus Crew beat 10-man Orlando City 2-0 after extra time on Saturday to reach the Eastern Conference final.
Columbus will face the winner of Saturday's other semi-final between FC Cincinnati and the Philadelphia Union in next week's game with a place in the MLS Cup final at stake.
The Crew had the upper hand for large stretches of the game and went close in the first half when midfielder Aidan Morris saw his shot pushed wide by Orlando keeper Pedro Gallese and then Hernandez blasted just wide after good work from the lively Diego Rossi.
Orlando were defending valiantly and threatened at times on the break, but they found themselves a man down in the 78th minute when Argentine defender Rodrigo Schlegel was sent off for a second yellow card when he bundled down a goal-bound Rossi.
Columbus pushed forward in search of the winner but they almost got caught out at the break when a poor header from Rudy Camacho fell to Facundo Torres who fed Martin Ojeda only for the Argentine to fire his shot wide.
Columbus coach Wilfried Nancy introduced Ramirez for extra-time and within two minutes the moved had paid off handsomely.
Morris won the ball on the edge of the box, burst down the right and fired in a low cross which Ramirez slid into the net from close range.
Orlando responded positively though with Kyle Smith forcing Crew keeper Patrick Schulte into a fine save with his left leg after being put through by a beautiful pass from Junior Urso.
Schulte then did well to keep out an effort from Ramiro Enrique and then delivered a magnificent reaction save to keep out an Enrique header.
But deep in the second period of extra-time, Gallese was caught out when he had pushed up near the half-way line and Hernandez rounded him and fired into the unguarded goal from over 50 yards out.
Sunday's Western Conference semis see Houston host Sporting Kansas City before defending champions Los Angeles FC travel to two-times champions Seattle Sounders.
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