STANFORD, Calif. (AP) American Alison Riske changed her schedule this season to include the Bank of the West Classic for a variety of reasons. One of them was to change her luck.

The 59th-ranked Riske did just that, beating third-seeded Carla Suarez Navarro 6-4, 6-4 on Wednesday to reach the quarterfinals.

''I've had a lot of good matches against top players that have helped my confidence,'' Riske said. ''I wasn't winning but I was playing good tennis.''

It was a tough day for seeded players. No. 69 Ajla Tomljanovic beat the seventh-seeded Madison Keys 1-6, 6-4, 6-1 and Germany's Mona Barthel topped sixth-seeded compatriot Andrea Petkovic 5-7, 6-2, 7-6 (4).

Eighth-seeded Elina Svitolina survived the day in the final match, beating Stanford grad Nicole Gibbs, 6-3, 7-6 (5).

''That was tough. I thought I'd be off that court in 35 minutes,'' Tomljanovic said. ''She played so well in the first set, I felt like I wasn't even in it.''

Tomljanovic refocused on holding serve and eventually got herself back into it.

''I'm already considering this a great week,'' Tomljanovic said. ''When you go through bad stretches, you learn to appreciate wins even more.''

Barthel, who has lost her first round match in 12 of 17 tournaments played this year, could next play top-seeded Caroline Wozniacki, who makes her first appearance Thursday night.

Keys, who served nine aces, was playing her first event since reaching the quarterfinals at Wimbledon.

Riske, making her main draw debut in the event, beat a top-10 player for the first time in nearly two years and the second overall in 12 tries.

''I always like playing in California,'' Riske said. ''I wish there were more tournaments here. The weather is perfect and I played here my first year on the tour and enjoyed it. I needed to change my schedule.''