MADRID — The U.S. Open lost some more star power Friday — Rafael Nadal is gone, undone by a chronic foot injury that will sideline him for the rest of the season.

His announcement further depletes the year’s last major tennis tournament, with Roger Federer already out as well as last year’s champion, Dominic Thiem.

Nadal’s absence also clears one more possible hurdle for Novak Djokovic, who now resumes his bid for a calendar-year Grand Slam without one of his longtime rivals in the men’s draw at Flushing Meadows.