Stephens, Keys and Gauff lose in Washington; Venus' struggles continue in California

Sloane Stephens was beaten by Rebecca Peterson in a surprise loss at the Citi Open, while two other seeds Hsieh Su-wei and Monica Puig encountered no problems as they advanced to the second round.

American Sloane Stephens, the 2015 champion, was the top seed at the Citi Open.   -  Getty Images

Top seeds Sloane Stephens and Madison Keys suffered shock first-round losses at the Citi Open, while Coco Gauff also departed on Tuesday.

Stephens, the 2015 champion and top seed, went down to Swede Rebecca Peterson 6-2 7-5 at the WTA International event in Washington.

Peterson managed to break Stephens' serve five times on her way to an upset win over the world number eight.

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Keys was also stunned, losing to 17-year-old wildcard Hailey Baptiste, who was playing her first WTA Tour main-draw match and claimed a 7-6 (7-4) 6-2 win.

In main-draw action for the first time since her incredible run to the last 16 at Wimbledon, 15-year-old Gauff bowed out with a 6-4 6-2 loss to Zarina Diyas.

While Stephens and Keys were upset, two other seeds – Hsieh Su-wei and Monica Puig – encountered no problems.

Hsieh brushed past Kirsten Flipkens 6-4 6-3 and Puig was too good for wildcard Allie Kiick 6-4 6-2.

Kristina Mladenovic beat Shelby Rogers 6-4 6-4, wildcard Catherine Mcnally overcame Zhu Lin 6-4 6-2 and Camila Giorgi got past Sachia Vickery 6-2 7-5.

Venus' struggles continue, Azarenka eases through at Silicon Valley Classic

Venus Williams' tough run of form continued with a first-round loss to Bethanie Mattek-Sands at the Silicon Valley Classic, while Victoria Azarenka cruised through.

Williams has won just two matches since the French Open and the American veteran went down to Mattek-Sands 6-7 (4-7) 6-3 6-1 in a battle of the wildcards at the WTA Premier tournament in San Jose, California on Tuesday.

 

The seven-time grand slam singles champion had won her previous four matches against Mattek-Sands, but that run came to an end.

Azarenka, meanwhile, is continuing to enjoy a fine season and was untroubled by qualifier Harmony Tan, winning 6-2 6-4.

The two-time Australian Open champion set up a last-16 clash with Donna Vekic, the Croatian fifth seed having overcome Misaki Doi 6-4 3-6 6-4.

Vekic was one of two seeds in action, with Danielle Collins also progressing, getting past Zhang Shuai 6-4 5-7 6-2.

Meanwhile, Zheng Saisai hammered Heather Watson 6-3 6-1 and Madison Brengle breezed past Andrea Petkovic 6-0 6-3.