Kristina Mladenovic is into her first Grand Slam quarter-final after beating Ekaterina Makarova 7-6 4-6 6-1.
The Frenchwoman, ranked 40th in the world, struggled early on in the first set as Makarova started well with a break of serve. However, she soon found her feet in the match and forced the 13th seed to a tiebreak, where she simply fell apart, allowing Mladenovic to take the first set.
Things were more closely fought in the second set, but Makarova eventually came out on top when she broke as her opponent was serving to stay in the set, the 22-year-old unable to remain composed in the pressure situation as the match went to a decider.
Nonetheless, Mladenovic was the definition of cool in her third set performance, breaking three times and allowing Makarova to win just one game as she blazed through to the quarter-finals of the 2015 US Open.
Mladenovic fights hard to take opening set on tiebreak
It was Makarova who started well on Sunday, immediately breaking her opponent's serve after a sloppy opening game from the Frenchwoman. Mladenovic tried to fight back in the following game, but the 13th seed defended break points well to consolidate her lead.
Makarova continued to look good for her lead despite her opponent becoming more comfortable in the match, with a love service game from the Russian showing no signs of struggle and no threat from Mladenovic to break back.
However, the 22-year-old would fight back, drawing an error from Makarova to break back at 3-3, before picking herself up once more to level at 4-4 after she was broken to love just moments after getting the set back on serve.
Both pushed their opponent on their serve to try and sneak ahead and avoid the tiebreak, but neither were able to do so, with some strong serving taking us to 6-6 in the first set.
Mladenovic then dominated the tiebreak, taking a 2-0 lead after a poor smash from Makarova, which soon turned into a 5-1 advantage and a one set lead for the Frenchwoman. Makarova had handed her opponent the lead with several sloppy errors, but she would not be panicking just yet, as she had won both of the two's only two previous encounters from a set down.
Youngster loses composure when it matters the most as Makarova levels the scores
The second set was bound to be a lot tighter, with Makarova having little room for error and Mladenovic not wanting to squander a strong lead.
Both served well from the off, and battled hard when they needed to, producing the goods in pressure situations. Most of the games in the set saw the receiving player tot up no more than one point, whilst aces and strong winners were aplenty as both exhibited real quality in what was becoming an exciting encounter.
Makarova put the pressure on her opponent right at the end of the set though, a love service game from the Russian forcing Mladenovic to serve to stay in the set - and it was pressure that the 22-year-old could not handle.
The Frenchwoman opened the crucial game with a double fault, whilst her opponent was fired up and ready to take the game to her, eventually breaking to love to win the second set, level the scores and take the match to a decider.
Mladenovic keeps her cool to win it, whilst her opponent falls apart
The momentum appeared to be with the experienced and higher ranked Makarova from here, as she served to open the deciding set.
However, proceedings went in the complete opposite direction as Mladenovic capitalised on numerous errors by the Russian in the first game to break immediately.
The 22-year-old consolidated this with a strong service game, before establishing a double break lead. Makarova was falling apart on Arthur Ashe now, more errors from her and opportunistic play from her opponent seeing the score read 3-0, which quickly became 4-0.
The Russian finally got herself on the board for the set in the following game, coming from two points down to do so, but it was all far too little, far too late.
Mladenovic was much more composed as we neared the end of this set, forcing Makarova to serve to stay in the tournament, and the 13th seed was unable to do so, with Mladenovic fighting hard to get the match over and done with on her opponent's serve, and getting her reward as she won the third set 6-1 thanks to three breaks, sealing her place in the last eight.
Semi-finals a real possibility for the 22-year-old
She may just be into her first ever Grand Slam quarter-final now, but there is a real chance that Mladenovic can go one better and make the last four, with her drawn against Roberta Vinci, who made it to this stage thanks to Eugenie Bouchard's withdrawal from the tournament due to concussion.
The 32-year-old Italian, ranked 43rd in the world, has plenty of experience though and will be a tough opponent for Mladenovic. Vinci has made it to the last eight of the US Open three times in the last four years now, and knows what it takes to perform on the biggest stage having won all four Grand Slams as a doubles player - her victory at Flushing Meadows coming back in 2012.
The two have never met before, but present an interesting match-up - the only one between two unseeded players as well. The winner of their encounter is then likely to face world number one Serena Williams, searching for her first Calendar Grand Slam, granted that her sister, Venus, does not thwart her in the last eight.