BASTAD, Sweden - Down a break in the final set, top seed Caroline Wozniacki battled into the quarterfinals of the Ericsson Open on Thursday, defeating Viktorija Golubic, 6-2, 2-6, 6-4. 

Winning from 2-0 down in the final set for the second straight match this week, Wozniacki's victory marked her 40th win on the WTA this season - the first player to reach that milestone.

Read more: Inside the Numbers: Wozniacki becomes first to 40 wins

"I just kept my head down and tried to stay aggressive," Wozniacki said. "I was going for it and making quite a few mistakes especially in the second set...eventually [the ball] has to start going in, and it did. I just kept going for my shots."

Each player broke twice en route to splitting the first two sets, as Wozniacki saved both break points set faced in the first and Golubic responded in kind to the only opportunity that the top seed created in the second ret.

The World No. 102's momentum continued to begin the decider, as she raced out to a 0-40 lead on Wozniacki's serve, only to break on her fourth chance - taking advantage of some uncharacteristic mistakes off of Wozniacki's racquet. 

The top seed found her form as the decider wore on, as she won four straight games to turn a 0-2 deficit into a 4-2 advantage, but Golubic hit back and knotted the action at four games apiece after breaking and holding in a pair of lengthy deuce games. 

However, Wozniacki made one last push to punch her ticket to the quarterfinals, as she held serve to move one game away from victory, and played a composed final game for her fifth break of the match.

Wozniacki struck 36 winners over the course of the one hour, 50-minute encounter, managing to stay in the positive with 24 unforced errors.

Golubic also played a composed and tidy match from her side, posting 19 winners to 13 unforced errors, but the Dane proved more efficent on break points. The top seed converted on five of her nine chances in the match, while Golubic won just four of 10 - going just 2/8 in the two sets she lost. 

The Dane will face Ukrainian qualifer Kateryna Kozlova for a spot in the semifinals, as she overcame both a mid-match rain delay and former champion Mona Barthel, 6-3, 6-3.

"Four matches, it's good for me - so I'm very excited," the Ukrainian qualifier said. "It was a tough draw - she's a very tough opponent. I was trying to focus on my game, to do my best on court. I expected a tough match because Mona is a very tough player, so I'm happy that I could finish like this. 

"I'm excited [to play Caroline.] I've never played against her and I haven't played many matches against the top 10. I'll be happy to play the next round against her, and I'm waiting for the match."

Wozniacki was the lone seed to advance to the quarterfinals on Thursday, as Belgian Elise Mertens dispatched No.5 seed Carla Suarez Navarro, 6-3, 6-7(2), 7-5 in nearly three hours to open the day's play in Bastad. In addition, the rematch of the final from the Nürnberger Versicherung did not take place as scheduled, as No.6 seed Kiki Bertens gave a walkover to Czech Barbora Krejcikova. 

Friday's quarterfinals see Krejcikova face No.3 seed Caroline Garcia, No.7 seed Katerina Siniakova face No.2 seed Anastasija Sevastova, and Mertens face Serbia's Aleksandra Krunic.