Japan’s Kei Nishikori retired from his French Open tennis second-round match with a sore right shoulder Thursday after dropping the first two sets to rising U.S. star Ben Shelton 7-6(7), 6-4. The injury-plagued former world No. 4, who was playing his first Grand Slam since the 2021 U.S. Open, decided to stop as the match was interrupted by rain after the second set. Shelton hit 33 winners, while racking up nine aces to Nishikori’s none. Nishikori’s loss left no Japanese in the men’s or women’s singles draw at Roland Garros. “The pain began to increase midway through the second set,” Nishikori …