Juan Martin del Potro, of Argentina, shakes hands with Rafael Nadal, of Spain, after Nadal retired from the match during the semifinals of the U.S. Open tennis tournament, Friday, Sept. 7, 2018, in New York. (AP Photo/Adam Hunger)

Injured Nadal stops, putting del Potro back in US Open final

September 07, 2018 - 4:44 pm

NEW YORK (AP) — Defending champion Rafael Nadal retired from his U.S. Open semifinal against Juan Martin del Potro because of a painful right knee after dropping the opening two sets.

The No. 1-ranked Nadal was trailing 7-6 (3), 6-2 after two hours of play on Friday when he quit.

That allows del Potro to return to a Grand Slam final for the first time since he won the 2009 U.S. Open. Since that lone championship, the 29-year-old del Potro has needed four wrist operations, which slowed his career trajectory.

The third-seeded Argentine will face Novak Djokovic or Kei Nishikori in Sunday's final.

Nadal had been trying to win a fourth U.S. Open title and 18th Grand Slam trophy overall.