NEW YORK • Novak Djokovic opened the defence of his US Open title with a 6-3, 5-7, 6-2, 6-1 first-round win over Poland's Jerzy Janowicz on Monday, but the laboured performance gave rise to fresh concerns about the world No. 1's fitness.

There were plenty of signs of trouble, starting with a visit from a trainer who massaged his bothersome arm after only five games.

Asked about his health during an on-court interview, Djokovic said: "I don't think it's necessary to talk about this now. I'm through. I'm taking it day by day."

During the match, he hit first serves around 160kmh and sometimes slower - 40kmh or so below his usual average speed.

He hit second serves in the low 80s. He flexed his right arm, the one he has used to wield a racket on the way to 12 Grand Slam titles, and appeared generally unhappy.

This was the world No. 1's first match at a major tournament since losing to Sam Querrey in the third round of Wimbledon, which ended the Serb's bid for a calendar-year Grand Slam after titles at the Australian Open and French Open.

Heading into the US Open, Djokovic had to deal with a left-wrist injury that flared up before the Rio Olympics this month.

But that wrist appeared to be fine against Janowicz, a former top-20 player who reached the semi-finals at Wimbledon in 2013 and is now ranked 247th after his own series of injury issues.

Djokovic might have been in trouble on another day at Flushing Meadows but Janowicz has advanced beyond the first round just once in four previous visits here.

Several times during the 2hr 37min match, the Serb could be seen grimacing when hitting his powerful forehand.

"It was just prevention, it's all good," he said after the match.

"Look, each day presents us some kind of challenges and after all I've been through in the last couple of weeks it's pleasing to finish the match and win it."

Up 3-2 in the opening set, Djokovic called for a medical timeout during the changeover and had his forearm massaged.

When play resumed, he immediately broke the Pole and held serve on his way to taking the first set.

But in the second set, Djokovic's discomfort became even more evident as he double faulted and then sent a wild forehand long as Janowicz broke to take control and level the match.

Normal service was resumed in the third and Djokovic moved in for the knockout punch, breaking Janowicz to open up the fourth set before wrapping up the match.

A US Open finalist in five of the last six years, Djokovic next faces Czech Jiri Vesely, a five-set winner over Indian qualifier Saketh Myneni.

Earlier in the Arthur Ashe Stadium, Rafael Nadal, another two-time US Open champion (2010 and 2013), won his first Grand Slam match in three months.

The Spaniard cruised to a 6-1, 6-4, 6-2 win against Denis Istomin and unravelled the thick wrap of white tape protecting his left wrist following an injury.

He said he is still not back to his best, but there was nothing that seemed to be as debilitating as what Djokovic went through.

REUTERS, THE GUARDIAN

US OPEN: DAY 3
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