NEW YORK — Juan Martin del Potro is through to his second career Grand Slam final and first since 2009.
The big Argentine was leading 7-6 (3), 6-2 when Rafa Nadal retired with a right knee injury.
Nadal took a medical timeout for treatment after falling down a break, 1-2 in the second set, and was not moving at 100% thereafter. The Spaniard had spent nearly 16 hours on court in the five matches leading up to this match, the most of any semifinalist by a wide margin.
Del Potro will face the winner of Friday's second semifinal between Kei Nishikori and Novak Djokovic on Sunday.