NEW YORK—Novak Djokovic’s bid for the first calendar-year Grand Slam in men’s tennis since 1969 ended one victory short with a 6–4, 6–4, 6–4 loss to Daniil Medvedev in the U.S. Open final on Sunday. Medvedev’s surprisingly lopsided triumph gave him his first major championship and prevented Djokovic from winning what would have been the record 21st of his career. The No. 1-ranked Djokovic entered this match 27–0 in 2021 at the sport’s four most important tournaments, enduring the burdens of expectations and pressure that came along with his two-track pursuit of history over the past seven months and, in New York, the past two weeks. He beat Medvedev in the Australian Open final on a hard court in February, then added titles on clay at the French Open in June and Wimbledon on grass in July. But Djokovic, a 34-year-old from Serbia, couldn’t get to 28–0. He simply was …