MADRID -- Mirra Andreeva enjoyed the happiest of birthdays on Monday at the Mutua Madrid Open. The newly-turned 17-year-old phenom came from 5-2 down in the first set to defeat 12th seed Jasmine Paolini 7-6(2), 6-4 in the Round of 16. 

Andreeva is the second-youngest player to reach a WTA 1000 quarterfinal since the format was introduced in 2009. Coco Gauff reached the quarterfinals at 2021 Dubai at 16 years old. Andreeva is one of just four players to have reached a WTA 1000 quarterfinal before their 18th birthday, joining Anastasia Pavlyuchenkova, CiCi Bellis and Gauff.

"I do feel old, to be honest," Andreeva said. "I don't know what scares me [about getting older], but I just want to stay the same person that I was. But I know that age is not something that I should look at too. I think I will always stay the same person but the time has passed quickly."

The victory earned the 43rd-ranked Andreeva her first WTA 1000 quarterfinal, going one round further than her fourth-round showing in her tour debut 12 months ago. 

"I'm always happy with each win," Andreeva said. "I cannot say that this feels different. It feels like another match. I don't have any expectations or any pressure. I will just play with the same mindset, the same everything that I did before, and we will see."

Andreeva will face either No.2 and defending champion Aryna Sabalenka or No.15 Danielle Collins for a spot in the semifinals.

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Facing Dubai champion Paolini for the first time, Andreeva struggled to hold her serve through the early stages. Coming off a confident straight-set win over Caroline Garcia in the previous round, Paolini broke Andreeva in her first three service games to build a 5-2 lead. 

But after saving one set point to hold to 5-3, Andreeva slowly turned the match around. She cleaned up her errors and took advantage of the deflated Italian's dip. Andreeva came through another tight deuce game to take the set to a tiebreak and raced away to complete her comeback. 

The second set nearly saw a reversal of fortune. Andreeva led 4-0 with a point for 5-0, but this time it was the teenager's turn to flinch as the match neared the finish. Paolini put the set back on serve at 5-4, but could not hold serve to maintain her comeback pressure. Andreeva broke serve on her first match point as Paolini put a forehand just long of the baseline. 

Andreeva's win over Paolini was her third consecutive win over a seeded opponent and second over a Top 15 player this week. After defeating No.58 Taylor Townsend in the first round, Andreeva has ousted No.29 seed Linda Noskova of the Czech Republic, No.7 and reigning Wimbledon champion Marketa Vondrousova, and Paolini.Â