HUA HIN, Thailand -- No.1 seed Garbiñe Muguruza of Spain reached her first quarterfinal of 2019 after maneuvering past dangerous German Mona Barthel, 6-3, 7-5, on Wednesday night at the Toyota Thailand Open presented by E@.

In their two previous meetings, Barthel had defeated Muguruza in a Challenger final in 2011, but Muguruza won their only WTA-level meeting, at 's-Hertogenbosch in 2013. The former World No.1 started an undefeated streak against Barthel at WTA events by claiming the win in Hua Hin after one hour and 18 minutes of play.

The Spaniard had to recover from 0-4 down in the second set before winning seven of the last eight games of the clash. Muguruza converted six of her nine break points in the match, while Barthel was undone by ten double faults, many coming at inopportune times.

"I was expecting that she’s going to make great shots and great serves, so I didn’t get frustrated," Muguruza said, during her on-court post-match interview. "I just continued playing -- I know that if I continue, I’m going to have my chance. That’s pretty much what I did."

Muguruza will face No.8 seed Dayana Yastremska of Ukraine in the quarterfinals. 18-year-old Yastremska, who made her Top 50 debut on Monday, dispatched former Top 20 player Peng Shuai of China, 6-1, 6-4, earlier on Wednesday.

Yastremska beat Muguruza in their only prior meeting, in Luxembourg last year. "All the matches here are very tough, because there’s a lot of good players," Muguruza admitted. "I’m just looking forward to playing as many matches as possible."

Barthel started the tilt inauspiciously, blasting four errors in the first game to be broken at love. The German, however, found some fearsome forehands to strike back immediately, breaking Muguruza to level the set at 1-1.

But that would turn out to be the only time Muguruza faltered in the opening frame, as the Spaniard took command of the set by breaking for 3-2 as Barthel fired another flurry of errors. Muguruza started to control her service games with ease, slamming a service winner to hold for 4-2, then forcing an error with a lob to lock up a 5-3 lead.

Barthel was unable to recover from there, and hit three double faults in the last game of the set, including in the final two points, to hand the opening set to Muguruza. The Spaniard won 10 of her 11 first-service points in the set, while Barthel was undone by 15 unforced errors, nearly double that of Muguruza’s miscue total.

Barthel, though, had designs on extending the encounter into a third set. The German began to blast winners at ease, particularly with her forehand, and dominated Muguruza in the Spaniard’s early service games. Barthel won eight of Muguruza’s first nine service points in the second set as she zoomed ahead to a seemingly insurmountable 4-0 lead.

It appeared for all the world like Barthel had fully wrested the momentum away from the top seed, but, following a coaching visit from Sam Sumyk, Muguruza started to ease her way back into the match. Solid returning from the Spaniard helped to extend points, and Barthel found herself with more unforced errors again.

Barthel dropped serve at love at 4-1, double faulting on break point. The German then squandered two game points at 4-3, hitting consecutive double faults to get broken again. Muguruza held to win five straight games, and while Barthel held for 5-5 to stop the streak, strong passing shots and backhands by Muguruza allowed her to break the German once more for the win.