Wickmayer, who is ranked 37th in the world and reached the third round at Wimbledon, is looking for her first WTA title this year and the fourth of her career.
She reached the quarterfinals at Stanford two years ago.
Chang played her first main-draw match in a month. She qualified for the Australian Open and won her first-round match before losing to Jelena Jankovic.
In other matches, sixth-seeded Chanelle Scheepers beat qualifier Grace Min 6-4, 6-4, and Michelle Larcher De Brito defeated Australia's Jarmila Gajdosova 5-7, 6-2, 6-3.