NEW YORK -- Novak Djokovic double-faulted, then shook his right arm and grimaced.Seconds later, a weak serve produced a wince from the US Opens defending champion, then was followed by a missed forehand that gave away a set -- the first set dropped by Djokovic in the first round of any Grand Slam tournament since 2010.While he managed to emerge with a 6-3, 5-7, 6-2, 6-1 victory Monday night over Jerzy Janowicz of Poland, there were plenty of signs of trouble, starting with a visit from a trainer who massaged Djokovics bothersome arm after only five games.Asked about his health during an on-court interview, Djokovic deflected the question, saying, I dont think its necessary to talk about this now. Im through. Im taking it day by day.When the subject arose at his news conference, Djokovic again avoided addressing the topic, saying the trainers visit was just prevention; its all good.During the match, Djokovic hit first serves around 100 mph, sometimes slower -- 25 mph or so below whats normal for him. He hit second serves in the low 80s. He flexed that right arm, the one he has used to wield a racket on the way to 12 Grand Slam titles, and appeared generally unhappy, covering his head with a white towel at changeovers.Djokovics coach, Boris Becker, gnawed on his fingernails, looking as nervous as can be.All in all, Djokovics issues figure to loom large as the tournament progresses and were the most noteworthy development on a Day 1 at Flushing Meadows that did include drama elsewhere.There was 20th-seeded John Isners comeback from two sets down to edge 18-year-old Frances Tiafoe before a rowdy, standing-room-only crowd at the new Grandstand. And 26th-seeded Jack Socks five-set victory over 18-year-old Taylor Fritz in another all-American matchup.In other earlier matches, 2014 US Open champion Marin Cilic beat 108th-ranked Rogerio Dutra Silva 6-4, 7-5, 6-1, despite posting more unforced errors than winners (24-23). Britains Kyle Edmund, in his US Open debut, upset 13th-seeded Richard Gasquet 6-2, 6-2, 6-3.This was the No. 1-ranked Djokovics first match at a major since losing to Sam Querrey in the third round of Wimbledon, which ended the Serbs bid for a calendar-year Grand Slam after titles at the Australian Open and French Open. He exited the Rio Olympics in the first round this month, then sat out the Cincinnati Masters because of a sore left wrist.After all Ive been through in the last couple of weeks, its pleasing, of course, to finish the match and win it, said Djokovic, who lost to his next opponent, Jiri Vesely, at Monte Carlo in April. Look, each day presents us some kind of challenges that we need to overcome, accept and overcome.The left wrist appeared to be just fine against Janowicz, a former top-20 player who reached the semifinals at Wimbledon in 2013 and is now ranked 247th after his own series of injuries.Earlier in Arthur Ashe Stadium, Rafael Nadal stood near the net after winning his first Grand Slam match in three months -- 6-1, 6-4, 6-2 against Denis Istomin -- and unraveled the thick wrap of white tape protecting his all-important left wrist. He said hes still not back to hitting his forehand the way he does when hes at his best.Nadals afternoon match was played with the new $150 million retractable roof open under a blue sky, while offering some extra shade on a day when the temperature reached 90 degrees.The good news, Nadal said afterward, is that the pain is gone from his wrist, which whips those violent, topspin-heavy forehands that are the key to his success -- 14 of his 21 winners came off that wing.The bad news for Nadal?He still is working on feeling comfortable hitting down-the-line forehands, after sitting out -- not just zero real matches, but barely any practice, either -- from his withdrawal at the French Open in late May to the Olympics.Not easy to go 2? months out of competition, in the middle of the season, without hitting a forehand, Nadal said. I need to have the confidence again with my wrist.Both Nadal and his coach, his uncle Toni Nadal, described the way Rafael changed the way he hits a forehand during the Rio Games to try to avoid pain.Both said things are improving.But as Toni noted: We need a little time.Istomin, ranked 107th, was not likely to give Nadal much of a test. So what did he think of Nadals play Monday?For the first set, I was feeling that he was not hitting hard, Istomin said. A lot of short balls.Nadals summation of his day: Not very good, not very bad.The Associated Press contributed to this report. Custom Cardinals T-shirts .S. hockey team after paying his dues as an NHL general manager for more than three decades and giving up a lot of his free time to help USA Hockey. 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With their top three point guards and Kobe Bryant all sidelined by injury, the Lakers signed Marshall out of the D-League on Friday before their home game against Minnesota. Rob Andrew, the former England rugby union fly-half and long-term professional rugby director at the RFU, has been unveiled as the new chairman of Sussex.Andrew, 53, played first-class cricket for Cambridge University between 1982 and 1985, and also turned out for Yorkshires second XI as a batsman and offspinner.His rugby career included 71 caps for England and five for the British and Irish Lions. He played in three World Cups between 1987 and 1995, before spending ten years at the RFU, eventually leaving at the end of last season.He succeeds Zac Toumazi as Sussexs chief executive at a tricky period in the clubs long history. The club was relegated at the end of 2015, bringing to an end a period of unprecedented success including three County Championships between 2003 and 2007, and with the ECB turning its attention towards the new city-based league scheduled to be launched in 2020, Andrews high-profile appointment is intriguingly timed.He will take over at Sussex Cricket in January 2017, with a brief to build on Toumazis work in overseeing the integration of the professional club with the recreational board annd its 245 affiliated league clubs.dddddddddddd.Commenting on the appointment, Jim May, chairman of Sussex Cricket said: I am extremely pleased about the appointment of Rob Andrew. He has exceptional experience, both playing and administering sport which will be of great help to our cricket management delivering success.I am thrilled and really excited to be joining Sussex, said Andrew. The structures that have been put in place under the Sussex Cricket Limited umbrella have laid a very strong foundation for the future.I am looking forward to working with everyone connected with Sussex to help create success in professional cricket, recreational cricket and community programmes and ensuring that Hove remains a very special cricket ground.I will be focussing on driving forward the strategy over the next few years and helping write the next chapter in the rich history of Cricket in Sussex. These are exciting times for Sussex Cricket and cricket in general and I cant wait to get started. ' ' '