STANFORD, CA, USA - The No.7 seed Lesia Tsurenko was the first to progress to the second round as she opened play at the Bank of the West Classic on Monday with a 6-3, 6-3 win over Spain's Lara Arruabarrena.

Breaking the Arruabarrena serve five times in the match, the World No.32 did not face a break point in the second set - and dropped a total of just eight points in five service games.

After trading breaks twice in the opener, it was Tsurenko who settled on serve to win the final three games of the set, and she converted on the lone break point opportunity she created in the second set to move through to the second round in an hour and 13 minutes. 

"I was nervous and also it's the first match on hard court," Tsurenko assessed in the victory. "Even when you practice, it's not the same because your opponent is trying to make your life as tough as possible, so you get all the different kinds of shots. The toughest part of today's match was just trying hit the ball somehow, but the thing I'm happy about is the serve."

The 28-year-old Ukrainian improved to 3-0 in her career against the Spaniard, having not lost a set, and was joined in the second round by a pair of teenagers: No.5 seed Ana Konjuh, 19, and unseeded 17-year-old Kayla Day.

Playing a match against an opponent nearly a decade her senior, Day looked composed from start to finish in a 6-4, 6-2 win over Japanese veteran Misaki Doi, and lost serve just once despite landing just 47% of her first serves in the one hour, 25-minute victory.

The win sets up a date with the top seed, and reigning Wimbledon champion Garbiñe Muguruza in the second round. The duo played earlier this year at the BNP Paribas Open in Indian Wells, where the teenager claimed the first set but ultimately fell in a decider. 

Looking toward the matchup, Day said: "[Muguruza] is obviously an unbelievable player and she's been playing really well, so I'm really excited to have a rematch against her. I love these courts and I love this entire city."

No.5 seed Konjuh progressed through to the second round as qualifier Marina Erakovic retired with injury with the Croatian leading 6-3, 1-0, while the last match of the day session sees Natlia Vikhlyantseva take on American Danielle Lao.