WASHINGTON -- Kei Nishikori pulled out of the DC Open on Tuesday because of an injured left knee shortly before he was scheduled to play what was supposed to be his first match at the second ATP tournament of a comeback from hip surgery.
Nishikori, a 33-year-old from Japan who was the 2014 U.S. Open runner-up, returned to top-level tennis last week in Atlanta. He reached the quarterfinals there before losing to eventual champion Taylor Fritz.
That was Nishikori's first ATP Tour event since October 2021. He had an operation on his hip in January 2022.
His ranking is No. 353 this week. Nishikori made it 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.
Nishikori was replaced in the draw in Washington by Sho Shimabukuro, who lost in qualifying.
Shimabukuro was scheduled to meet Lloyd Harris on Tuesday, with the winner moving on to face Wimbledon quarterfinalist Chris Eubanks in the second round at the hard-court tournament.