Aug 26 (Reuters) - Novak Djokovic may not have played any U.S. Open tune-up events but the Serbian will be the favourite in New York nonetheless as he looks to complete a calendar-year Grand Slam that would put him in rarefied air. A New York triumph would not only make Djokovic the first man since Rod Laver in 1969 to win the Australian Open, French Open, Wimbledon and U.S. Open in the same year but would also give him a record-setting 21st career Grand Slam title. The 34-year-old Serbian has spent much of his career in the shadows of tennis greats Roger Federer and Rafa Nadal but he is now level with the famed duo at the top of the list of men"s Grand Slam winners after a sensational year. Djokovic had looked imperious all season but has not competed since the Tokyo Olympics where he pulled out of the mixed doubles bronze medal match with a shoulder injury shortly after he was upset in the singles tournament at the same stage. "The level of tennis dropped also due to exhaustion, you know, mentally and physically," Djokovic said in Tokyo where a number of contenders struggled in sweltering conditions. Djokovic later cited a "taxing journey" since the start of the Australian Open in February for his reason to opt for rest instead of fine-tuning his game at any of the warm-up events ahead of the Aug. 30-Sept. 12 U.S. Open. Thankfully for Djokovic, his game is well-suited to the New York hardcourts, his preferred surface, given he is one of the top returners, has power from the baseline and athleticism that allows him to chase down balls most other players cannot reach. Since winning a third U.S. Open in 2018, Djokovic has only managed to reach the fourth round, most notably in 2020 when the tournament favourite swatted a ball in frustration that struck a female line judge which led to him being defaulted from the match. But with so much riding on this year"s U.S. Open, a rested Djokovic, who has triumphed at eight of the last 12 Grand Slam tournaments, will be laser-focused on the task at hand. Five players have achieved a calendar-year Grand Slam. Laver (1962, 1969) and Don Budge (1938) are the only men to accomplish the feat while nobody has done it since Steffi Graf became the third woman to achieve the feat in 1988.