(Reuters) - Former world number one Victoria Azarenka overpowered tournament qualifier Harmony Tan 6-2 6-4 to reach the second round of the Silicon Valley Classic in Northern California on Tuesday.
The Belarusian converted seven of her 12 break point opportunities to advance to the second round, where she will face fifth-seeded Donna Vekic of Croatia.
American Danielle Collins came out ahead in a marathon 6-4 5-7 6-2 battle with China's Zhang Shuai on a sun-soaked afternoon on the campus of San Jose State University.
The rising 25-year-old University of Virginia product said her conditioning was the difference in her first-round match.
"I think I did a really great job making it physical," Collins said.
"I've been working a lot on my fitness the last couple weeks after Wimbledon. I've had a good couple weeks of training and I think it paid off today."
Collins will next face Zheng Saisai after the Chinese defeated Britton Heather Watson 6-3 6-1 in their first-round match.
(Reporting by Rory Carroll; Editing by Amlan Chakraborty)