2014 US Open runner-up Kei Nishikori has pulled out of this year's tournament

Nishikori was replaced in the men's singles draw at Flushing Meadows by James Duckworth, who lost in qualifying.

Kei Nishikori, the 2014 U.S. Open runner-up, withdrew from the year's last Grand Slam tournament on Sunday after being sidelined all month with an injured left knee.

Kei Nishikori of Japan looks on in between serves against Taylor Fritz during the ATP Atlanta Open quarter finals at Atlantic Station (Getty Images via AFP)

Nishikori was replaced in the men's singles draw at Flushing Meadows by James Duckworth, who lost in qualifying. Duckworth will face Felipe Meligeni Alves on Tuesday in the first round of the U.S. Open.

The tournament begins Monday.

Nishikori is a 33-year-old from Japan who had an operation on his hip in January 2022. He returned to the ATP Tour in late July at Atlanta, where he won two matches to reach the quarterfinals before losing to Taylor Fritz.

Nishikori then missed an event in Washington, citing a problem with his left knee, and has not been back in action.

He was ranked as high as No. 4 in early 2015, about six months after his semifinal victory over Novak Djokovic at the U.S. Open made him the first male Grand Slam singles finalist from Asia.