INDIAN WELLS, CA, USA - No.20 seed Garbiñe Muguruza played some of her best tennis of the season to upset Kiki Bertens and book a spot into the BNP Paribas Open quarterfinals.

Muguruza had experienced a tennis resurgence during this Indian Wells fortnight, claiming all three sets she contested coming into the fourth round.

She got a big boost of confidence from her win in the last round, improving to 3-3 against Serena Williams after the former World No.1 was forced to retire in the second set trailing 6-3, 1-0 - while it lasted just over one set, Muguruza showed signs of a high quality tennis to claim her first win over a Top 10 player since Dubai 2018.

Read more: Muguruza advances to Indian Wells fourth round after Serena retirement

But it wasn’t a completed match, and Muguruza told press in Indian Wells that she still wanted more.

“It's really a weird feeling, because I don't feel like I won the match point and ‘Well done, you know, good match…’ I think I played well one set. I'm going to take the positive side of that. Now I have more chances to face top and top opponents. That's what I'm looking for.”

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Muguruza got the chance to correct that stat right away against No.7 Bertens. The Dutch player didn’t make things easy for Muguruza, but the No.20 seed recovered in style after dropping her opening set to win 5-7, 6-1, 6-3.

“I think it was a very tough match,” Muguruza told press after the win. “I think we both played well. Every rally was very intense, was very long. Basically until the end of the match, any of us could win.

“And I'm happy about the level I played, and also how I managed the intensity of the game and not let drop, basically, nothing during the whole match.”

Muguruza was playing some vintage tennis for the opening exchanges, looking very much like the giant-slaying player that lifted trophies at the French Open and Wimbledon. She was aggressive on the return, creating break opportunities on Bertens’ first three service games and getting the break at 2-1. Muguruza kept her nose in front at 4-3 after the pair traded breaks, dominating the rallies through most of the opening set.

But she wasn’t able to maintain that level as Bertens found her range towards the end of the set, extending her stay at 5-3 and breaking Muguruza as she served for the set putting them back on serve. A spate of unforced errors from the Spaniard gifted Bertens another break to claim the 70-minute opening set.

The Spaniard shook off the disappointment and responded strongly to halt Bertens’ five-game run and go on a six-game streak of her own, taking the second set 6-1.

The third set was just as tight as the first, with both players dialed in and playing their best tennis. They traded breaks early in the set, with Bertens earning a 2-1 lead and Muguruza recovering the deficit in the next game. They stayed toe-to-toe for the rest of the set, until Muguruza earned the decisive break in the final game, edging past Bertens in a marathon match point to claim the victory after two hours and 27 minutes.  

The win sends her back into the Indian Wells quarterfinals for the second time in her career, and it seals Muguruza’s first Premier Mandatory quarterfinal since 2017.

Up next, Muguruza will take on one of the most in-form players of the tournament as she faces 18-year-old Bianca Andreescu in the quarterfinals.

“I saw her play. I think she's playing very well since the start of this year,” Muguruza told press after the match. I don't know a lot about her. I think she's -- well, not around for a long time, so she's starting to play better and better. Yeah, it's going to be exciting.”