MIAMI, FL, USA -- Romanian qualifier Monica Niculescu pulled off an epic upset at the Miami Open on Friday, ousting No.20 seed Garbiñe Muguruza of Spain, 7-6(0), 4-6, 6-2 to advance to the third round in southern Florida.

"I love it here, I like the new stadium, I like all the facilities that we have, so I’m so happy that we’re here," Niculescu told the media, after her win. "Many Romanians [in the crowd], I had so much support and every ball they were cheering for me. I liked that I moved well, and I saw the court very good, and I could do amazing shots, so it was pretty good."

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Two-time Grand Slam champion and former World No.1 Muguruza had won their only previous match handily: a 6-1, 6-1 dismantling at Linz in 2016. But it was World No.138 Niculescu who held firm to pull through this three-set tilt and claim a Top 20 win after a grueling two hours and 54 minutes of play.

"I knew I played pretty good in qualies, and also the first match in main draw had great tennis, but it’s tough to play Garbiñe," Niculescu stated. "I played her before in Linz and I didn’t do too good.

"I’m happy that I came strong in the third, and I ran a lot today!"

Niculescu got the better of Muguruza's second serve in the match: the Romanian won two-thirds of points when returning that shot during the match overall. The combatants combined for 17 service breaks overall, but it was Niculescu who claimed the majority when they counted, facing and saving just a single break point in the decisive third set.

Niculescu will meet another former World No.1 in the third round: No.13 seed Caroline Wozniacki of Denmark, who beat Aliaksandra Sasnovich of Belarus, 6-4, 6-4 on Friday. Wozniacki has won all nine of their previous meetings.

The first set was a returner’s paradise, as 10 of the 12 games went against serve. Muguruza led 3-0 to start and served for the set at 5-4 and 6-5, but every time, Niculescu’s wily play pulled her level eventually.

This led to a dominant display in the tiebreak for the Romanian, when her incredible all-court play led her to a 6-0 lead and six set points. A terrific down-the-line winner gave Niculescu all seven points in the tiebreak as she pulled out the one-set lead.

The Romanian leapt ahead 2-0 in the second set before Muguruza punched through a break point with tremendous volley skills to level the set at 2-2. Both players then survived break points over the next few games before Muguruza dominated on Niculescu’s serve at 4-3, breaking at love to set up a chance to serve out the set.

Just as in the first set, Muguruza could not consolidate her break lead when trying to put the set away, and Niculescu used a dizzying dropshot to break straight back and get to 5-4. But errors from the Romanian in the following game suddenly led to a set point for Muguruza, and the Spaniard broke to level the match at one set apiece with an error-forcing forehand.

But all of Muguruza’s momentum was squandered in the very first game of the decider, when the Spaniard fired a plethora of unforced errors to drop serve at love. A hold at love to consolidate epitomized Niculescu’s grit and desire to win the match, as her incredible slices and dropshots were on song as the final set kicked off.

Muguruza dug herself a deeper hole, dropping serve at love again at 3-1 to give Niculescu a double-break advantage. Niculescu fended off a break point to hold for 5-1, then garnered three match points on Muguruza’s serve in that game via unforced errors by the former top-ranked player in the world.

Deep, powerful groundstrokes got Muguruza out of trouble in that instance, and the Spaniard held for 5-2. But, after double faulting away a fourth match point, Niculescu finished the match on match point number five, when Muguruza knocked a backhand into the net.