Novak Djokovic's quest to become only the third man to complete a calendar Grand Slam and first to win 21 majors started with a 6-1 6-7 (5-7) 6-2 6-1 victory over Holger Rune at the US Open.

Not since Rod Laver in 1969 has a man won all four majors in the same year – Djokovic arrived in New York as the Australian Open, French Open and Wimbledon champion.

Also eyeing history as the first man to claim 21 slams – currently tied with injured superstars Rafael Nadal and Roger Federer – Djokovic navigated his passage through to the second round at Flushing Meadows on Tuesday.

Danish qualifier Rune was making his grand slam main-draw debut, but the 18-year-old was not overawed under the bright Arthur Ashe lights.

However, Rune faded fast due to apparent cramps as world number one Djokovic eventually cruised through to round two of the year's final major after more than two hours.

Playing for the first time since his Golden Slam bid came unstuck at the Olympic Games in Tokyo, Djokovic looked comfortable initially, closing out a merciless opening set with an ace.

Djokovic did not face a break point, boasting 100 percent returns against first serve, barely giving Rune a break.

But that changed in the second set – the energetic Rune winding up the crowd as he raced out to a 3-0 lead before Djokovic swiftly reeled off four consecutive games to move ahead.

Rune, however, capitalised on some uncharacteristic double faults to ultimately level the match in a tie-break, much to the delight of the American crowd.

But that is as good as it got for a frustrated Rune, whose physical conditioning proved his downfall, having gone toe-to-toe with the top seed in a fearless display.

 

Data slam: Djokovic extends US Open streak

Back in New York for the first time since he was sensationally thrown out of the US Open last year after accidentally hitting a line judge in the throat with a tennis ball, Djokovic got the job done.

Three-time US Open champion Djokovic now remains unbeaten in opening-round matches at the tournament, with a 16-0 record.

 

WINNERS/UNFORCED ERRORS

Djokovic – 55/30
Rune – 24/26

ACES/DOUBLE FAULTS

Djokovic – 17/7
Rune – 1/4

BREAK POINTS WON

Djokovic – 8/14
Rune – 2/3