Serena Williams tough  battle against Bertens and wins 

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Serena Williams took another step towards her first calendar Grand Slam with victory over Kiki Bertens in the second round of the US Open.

The world number one trailed 4-0 in the opening tie-break but came back to win 7-6 (7-5) 6-3 at Arthur Ashe Stadium.

Top men's seed Novak Djokovic had little trouble overcoming Andreas Haider-Maurer 6-4 6-1 6-2.
But eighth seed Rafael Nadal was tested during his 7-6 (7-5) 6-3 7-5 victory over Diego Sebastian Schwartzman

The Spaniard, who trailed 5-3 in the first-set tie-break and fell a break behind in both the second and third sets, admitted he had to fight for the victory.
Elsewhere, defending champion Marin Cilic returned to the Arthur Ashe stadium for the first time since winning the title last year with a 6-2 6-3 7-5 win over Evgeny Donskoy.