John Isner, the U.S. tennis player nicknamed the ‘Marathon Man’ for playing the longest tennis match in history, today retired from the grass-court major with a knee injury after 15 minutes.Isner withdrew in the third game of his second-round match on Court 3 against Adrian Mannarino of France at the All England Club after he tweaked his left knee.The 18th-seeded player had been the highest-ranked American man left in the singles draw. Isner’s draw had opened up after the opening-round upset of two-time champion Rafael Nadal of Spain. The two had been scheduled to meet in the fourth round.Isner, who missed the Australian Open at the start of the season because of a knee ailment, beat France’s Nicolas Mahut in the first round of Wimbledon three years ago in a match that lasted 11 hours, 5 minutes.