US Open PHOTOS: Williams sisters, Murray, del Potro sail into second round

IMAGE: Serena Williams of the United States returns a shot to Ekaterina Makarova of Russia during her first round singles match during the US Open at the USTA Billie Jean King National Tennis Center. Photograph: Mike Hewitt/Getty Images).

World number one Serena Williams opened her US Open account with a tidy 6-3, 6-3 win over Ekaterina Makarova on Tuesday, to join her sister Venus in the second round of the year's final Grand Slam.

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Williams, whose status as world number one is under attack from several fronts, delivered a message that she will not be surrendering the top spot without a fight, needing just 63 minutes to dispatch the 29th-ranked Russian.

Germany's Angelique Kerber and Spain's Garbine Muguruza, who have both beaten Williams in slam finals this season, along with Poland's Agnieszka Radwanska, will all be eyeing the number one ranking should the American's bid for a 23rd Grand Slam title stall.

IMAGE: Serena Williams of the United States shakes hands with Ekaterina Makarova of Russia. Photograph: Mike Hewitt/Getty Images.

Williams has held the number one spot since Feb. 18, 2013 and will extend her streak to 186 consecutive weeks by the end of the US Open fortnight, tying the WTA record currently held by Steffi Graf.

Back on Arthur Ashe Stadium court for the first time since a shock loss to Italy's Roberta Vinci in last year's US Open semi-finals, Williams made quick work of Makarova to follow the lead of her sister Venus.

IMAGE: Venus Williams of the United States returns a shot to Kateryna Kozlova of Ukraine during her first round singles match. Photograph: Mike Hewitt/Getty Images.

Sixth-seeded Venus had provided the opening act for sister Serena when she outlasted Ukraine's Kateryna Kozlova 6-2, 5-7, 6-4 before turning over the Arthur Ashe Stadium court to her top-seeded sibling.

IMAGE: Andy Murray of Great Britain returns a shot to Lukas Rosol of the Czech Republic during his first round match. Photograph: Mike Hewitt/Getty Images

Second seed Andy Murray, looking ominous in all black, was the last of the five to progress with a late-night 6-3, 6-2, 6-2 victory over Czech Lukas Rosol, effortlessly advancing without facing a single break point.

"I served very well," said Murray, who set up a second round encounter against Marcel Granollers of Spain.

"It was a tough start to the match, he had a few chances early on but once I got the break up, I played well."

IMAGE: Juan Martin del Potro of Argentina serves to Diego Schwartzman of Argentina during his first round match. Photograph: Elsa/Getty Images

Former US Open champion Juan Martin del Potro looms as a danger man at the US Open after barreling into the second round in straight sets over fellow Argentine Diego Schwartzman.

Plagued by a serious wrist injury that handicapped him since his rousing five-set win over Roger Federer in the 2009 US Open final, del Potro returned to form at the Rio Olympics, where he reached the finals before falling to Andy Murray.

The 6-foot-6 (1.98 m) Argentine backed up his impressive Rio run by rifling in 11 aces in eliminating Schwartzman, claiming the third-set tiebreaker 7-3.

"I am so glad to be part of this tournament once again after three years," said del Potro, who was given a wild card to join the main draw and said he was lifted by the crowd support.

"Always, in every match here at the US Open, the crowd make me feels special. I really like the atmosphere down there."

Del Potro said he was still feeling the effects of his efforts in Rio, where he ousted world number one Novak Djokovic in the first round and number five Rafael Nadal in the semi-finals before losing to second-ranked Murray in four sets in the final.

"To be honest, I'm still feeling tired," said del Potro.

"It's not easy after a big, big challenge like I did in Rio. But this tournament is very special for me. I'm trying to keep calm, to keep focused, and look forward to go far.

"The people in Argentina, in my hometown, they know what (I) have been through to get there after my surgeries. It was a special moment for me. They really appreciate what I did to come back on tennis. They are proud to see me playing tennis again."

Del Potro said he was close to quitting the game.

IMAGE: Stanislas Wawrinka of Switzerland returns a shot to Fernando Verdasco of Spain. Photograph: Mike Hewitt/Getty Images

Two-times Grand Slam winner Stanislas Wawrinka dealt Fernando Verdasco a rare first-round loss at the US Open, sweeping aside the Spaniard in straight sets.

The third-seeded Swiss dominated the left-handed Verdasco with his punishing groundstrokes and solid service game to claim a measure of revenge with a 7-6(4), 6-4, 6-4 victory at Arthur Ashe Stadium.

Verdasco, ranked 46th, had won 12 of his 13 previous first-round matches at Flushing Meadows.

Wawrinka, winner of last year's French Open and the 2014 Australian Open, had trailed Verdasco 3-2 in head-to-head action after falling to the Spaniard in straight sets in the first round this year at the Queen's Club run-up to Wimbledon.

"I'm really happy. I think it was a great match, especially for first round," Wawrinka told reporters. "You never expect to play your best game and (be) full of confidence, but I think the level was quite high."

Wawrinka hit seven winners off his one-hand backhand among his 30 total for the match, blasted in seven aces and turned away all four break points held by the Spaniard.

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