WASHINGTON (REUTERS) - Top seed and former champion Sloane Stephens crashed out of the Citi Open in Washington as she suffered a stunning 6-2 7-5 first-round loss to Swede Rebecca Peterson on Tuesday (July 30), while teenager Cori "Coco" Gauff also fell in straight sets.
Stephens, whose best result this year was a run to the Madrid semi-finals in May, was misfiring from the start and never managed to settle into much of a groove in her first meeting with the Swedish world number 70.
Peterson enjoyed a dream start as she raced out to a 5-2 lead and ultimately took the opening set in 29 minutes when Stephens sent a routine backhand from the baseline into the net.
Stephens, who triumphed here in 2015, started to settle down in the second and led 5-4 but Peterson broke back to get back on serve and never looked back.
Up next for Peterson will be the winner of a Tuesday clash between American Sachia Vickery and Italian Camila Giorgi.
Gauff, the 15-year-old sensation who made a stunning run to the fourth round at Wimbledon and came through qualifiers to reach the main draw in Washington, fell 6-4 6-2 in the afternoon to Zarina Diyas of Kazakhstan.
The turning point came at the end of the first set as Diyas converted her fourth set point of the game when Gauff sent a forehand into the net.
That brought an end to a game that had lasted more than 10 minutes and left the youngster visibly frustrated.
Diyas held at love to start the second set and never looked back en route to the win before packed stands on a hot and humid day in the US capital.
Gauff did herself no favours, smacking her 33rd unforced error on match point having also given Diyas 16 break points, five of which she was able to convert.
Next up for Diyas is a second-round clash with fifth seeded Lesia Tsurenko.
Olympic champion Monica Puig also advanced with a 6-4 6-2 victory over American Allie Kiick and will face Russian Anna Kalinskaya in the second round.
On the men's side, Russian second seed Karen Khachanov will open the evening session against Frenchman Jo-Wilfried Tsonga in a second-round match followed by a first-round battle between Australian Nick Kyrgios and American Thai-Son Kwiatkowski.