Juan Martin del Potro will compete in his first Grand Slam final in nine years after defending champion Rafael Nadal retired injured from their US Open semi-final.
Argentine third seed Del Potro was leading 7-6 (7-3) 6-2 when Nadal quit because of a knee problem.
Top seed Nadal, 32, twice needed medical attention before walking off.
Del Potro, 29, last competed in a Grand Slam final when he won at Flushing Meadows in 2009.
Ironically he has suffered a catalogue of injury problems himself since, contemplating retirement after a series of wrist injuries before fighting back to his highest ranking this year.