Keothavong beaten in Brazil
British number four Anne Keothavong was beaten in the opening round of the Brasil Tennis Cup on Tuesday.
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The Londoner lost 6-3 6-4 to French seventh seed Kristina Mladenovic in Florianopolis.
Keothavong's bid was undermined by a poor first-serve percentage of 44 and she was duly broken on five occasions.
Mladenovic told the official WTA website: "In the match I focused on every shot, fought everything and found the rhythm, and I beat a very good player.
"I didn't expect to win this match.''
Having once been ranked inside the top 50, Keothavong is now down at 183rd on the WTA list.
The 29-year-old has won just one main-draw match at WTA level since Wimbledon last summer, although she did help Great Britain's Fed Cup team progress to the World Group II play-offs earlier this month.
Top seed Venus Williams eased into the second round with a straight-sets win over Mirjana Lucic-Baroni of Croatia.
The American, now back in the world's top 20, was particularly dominant on serve as she claimed a 6-3 6-3 victory in what was her first match since the Australian Open.
It could have been easier for Williams, though, as Lucic-Baroni fought back from 5-0 down in the second to 5-3, saving seven match points in the process.
"At 5-0 I was a little too confident and maybe playing a little too relaxed, but she also started playing really well and really aggressive on those match points," Williams said.
"She brought out her best tennis. It showed a lot of character from her. It's easy to give up when you're down 5-0, but she did really well to make it closer in the end. I knew it was just a matter of time before I got it, though."
Not all the seeds in action had it so easy as number three Kirsten Flipkens of Holland lost 2-6 6-4 6-4 to Olga Puchkova.
There was no such problem for fifth seed Magdalena Rybarikova though, as she beat Kimiko Date-Krumm in straight sets.
There were also first-round wins for Garbine Muguruza, Tatjana Malek, Timea Babos and local wildcard Beatriz Haddad Maia.
There was an upset in the day's only second-round match, as Jana Cepelova beat eighth seed Annika Beck 7-6 (8/6) 6-4.