NOTTINGHAM, Great Britain - In her WTA grass-court debut, No.5 seed Mihaela Buzarnescu blew hot and cold - but made the quarterfinals of the Nature Valley Open with a 6-3, 5-7, 6-3 victory over qualifier Irina Falconi.

This time last year, the Romanian was playing the ITF $60,000 event in Hodmezovasarhely, Hungary - where the biggest title run of her career at the time kickstarted a meteoric rise from No.374 to her current position of No.30.

Since lifting that trophy, Buzarnescu has compiled a 79-26 win-loss record that includes runner-up showings in Hobart and Prague this year - and is fresh off her first ever run to the second week of a Grand Slam at Roland Garros, where she stunned World No.4 Elina Svitolina in the third round. A confident start indicated that the Romanian has settled into her status as favorite as well, though.

Two double faults in the opening game put Falconi at a disadvantage immediately, but Buzarnescu was in control in most aspects of the game. The 30-year-old's short backswings are proving an asset on grass this week, enabling her to react quickly to the low bounce and to disguise her own shots, and consequently she would gain the upper hand in a number of stylishly constructed rallies.

Though the American, who was seeking to make her first WTA quarterfinal since Nurnberg 2016 (and first on grass since Birmingham 2012), would occasionally succeed in disrupting Buzarnescu's rhythm with short slices, a key difference would be the quality of each player's serve. Though both were landing a good number of first serves (79% for Falconi to 76% for Buzarnescu), the Hobart and Prague finalist's deliveries were simply much more effective, setting her up to win 63% of those points to Falconi's mere 52%.

Buzarnescu's aggressive approach to returning was also a relevant factor. Time and again, she would tee off, striking a number of clean winners off the Falconi serve - including en route to breaking the 28-year-old a second time to seal the set.

But a Buzarnescu lapse to open the second set, dropping serve with an errant backhand, paved the way for a more tightly contested passage of play in which the left-hander seemed to be battling herself as much as her opponent. As Buzarnescu's execution became inconsistent, her emotional focus also lapsed, and she would frequently berate herself after missed chances: an unconverted 0-40 lead to level the score in the sixth game and, even after managing to break back for 4-4, a pair of double faults that left Falconi serving for the set.

The climax of the set was edge-of-seat stuff, with Buzarnescu going all out and coming up with spectacular winners from behind - but littering her game with errors whenever she had a chance to move ahead. The World No.152, resolutely rushing the net, succeeded in putting more pressure on her opponent - and, serving for the set for a second time, withstood a barrage of all-or-nothing returns to stave off three break points and square the match on her second set point.

But some neat net play on Buzarnescu's part, as well as a return of her earlier scything forehand winners, demonstrated that she had been able to regroup. Eking out two consecutive breaks of serve, the only PhD holder on Tour worked her way towards a 5-0 lead, keeping her focus on crucial deuce points and capturing both break point opportunities at the first time of asking.

That would not be the end of the drama: a dogged Falconi would save three match points as she begun to claw her way back up the scoreboard as Buzarnescu's frustration began to boil over again - particularly when a dead net cord denied her the match.

Serving out the match a second time proved the charm, though - and a pair of service winners ended up sealing the deal for Buzarnescu in stress-free fashion at last. She will next face either No.3 seed Naomi Osaka or Denisa Allertova in a bid to reach her fourth WTA semifinal in the past nine months.