Battling Watson exits Montreal
British No 1 Heather Watson suffered a straight-sets defeat to Victoria Azarenka in the third-round of the Rogers Cup in Montreal.
Qualifier Watson, who knocked out 10th-seeded Dominika Cibulkova of Slovakia, was looking to continue her recent run of good form.
However, she was broken three times as she lost the first set 6-2, serving four double faults and winning less than half of points on her first serve.
She showed her fighting spirit by fighting back from a break down in the second to level at 3-3 - the first time she had ever taken three games in a set against Azarenka - but the Belorusian immediately broke again to lead 4-3 and closed the match out 6-2 6-4, finishing with an ace.
Top-ranked Serena Williams cruised into the quarter-finals with a 7-5 6-4 win over Lucie Safarova, while sister Venus ousted Angelique Kerber 6-3 3-6 6-4 at the Montreal tournament.
Playing in Montreal for the first time in 14 years, world number one Williams has looked at ease on the hardcourts after winning the tournament in Toronto last year.
"I really needed to serve well today because she was just hitting unreturnable serves to me," said Williams. "We didn't really have too many long rallies.
"We both were just hitting lots of service winners or aces. So it was kind of hard to get in a good rhythm."
Williams will now face Denmark's former world No 1 Caroline Wozniacki, who brought American qualifier Shelby Rogers' fairytale run to a 6-1 6-0 end.
Petra Kvitova, playing in her first event since winning her second Wimbledon title, fell 6-4 1-6 6-2 to Russia's Ekaterina Makarova while fourth seed Maria Sharapova was beaten 6-2 4-6 6-2 by Spain's Carla Suarez Navarro and American Coco Vandeweghe shocked Jelena Jankovic 7-6 (8) 2-6 7-5.