NEW YORK, NY, USA -- Three Americans had already booked their spots in the 2017 US Open quarterfinals. On Monday night, Madison Keys made it four.

In a scintillating battle between two 22-year-olds, it was No.15 seed Keys who came out the victor, outlasting No.4 seed Elina Svitolina of Ukraine, 7-6(2), 1-6, 6-4, in exactly two hours of play. Keys will now contest the first US Open quarterfinal of her career.

"It means the world to me to make the quarterfinals," said Keys during her post-match press conference. "It was a really rough start to my year. This is just amazing. You know, I'm really proud of myself for digging deep and figuring that out tonight."

"It's definitely more than just a win," Keys continued. "So often a match like that could have gone really quick for me, and I could have lost that third set fairly easy, come off and been really disappointed. So the fact that I dug deep and I figured things out, you know, I came out with a win means a lot to me. More than that, it just proves how deep I can dig and how hard I can fight."

Svitolina was looking for the World No.1 ranking after this event, but is eliminated from contention after this disheartening loss. Keys, on the other hand, joins Venus Williams, Sloane Stephens, and CoCo Vandeweghe in the quarterfinals -- and none of them are going head-to-head.

"I think it shows how hard we've been working," concluded Keys. "I'm really happy that none of us are playing each other in the quarterfinals. So yeah, I think if there's some all-American matchups in the rest of the tournament, I think that says really good things about women's tennis."

The first set started with both players finding opportunities on their opponent's serves: there were four breaks in the first seven games. Svitolina had additional chances at 4-4 to gain a break lead, but two break points fell by the wayside when the Ukrainian hit a backhand error on the first, and Keys hit an ace on the second.

The set marched into the tiebreak, where the American was completely dominant. Four consecutive winners, two of which came off Keys' vaunted forehand, opened the tiebreak, and within seconds, she had claimed a 4-0 lead.

A scorching service return winner gave Keys four set points at 6-2, and she converted the first one when Svitolina hit a return into the net. Keys was the aggressor in the first set, with 19 winners and 23 unforced errors, but the timing of those winners in the tiebreak was the reason she led by a set.

As impressive as Keys was in the tiebreak, Svitolina was even more so through the entirety of the second set. The World No.4 broke for 2-0 after a flurry of unforced errors by Keys, and by the middle of the set, Svitolina was zoning on her service return, as she hit a backhand winner off of a Keys serve to break again for 4-0.

An ace gave Svitolina a 5-0 lead in the set, and though Keys finally won a game with an ace of her own, a drop volley on Svitolina's first set point knotted the match at one set apiece. Svitolina was using her speed to hit outstanding shots from various points on the court, and she nearly matched the powerful Keys in winners in the 24-minute set.

The first two games of the deciding set, which featured tremendous rallies and both servers saving break points, were portentous of the rollercoaster to come. Keys began to move forward as much as possible, hoping to quell Svitolina's momentum from the second set by ending points early at the net.

At first, this seemed to be a poor strategy, as Svitolina was finding successful passes and angles, and got the first break of the set to lead 3-2. But the Ukrainian's first serve percentage was dipping, and her second serve velocity was starting to plummet, which gave Keys more confidence on her service returns.

"I definitely felt like I kind of hit a wall at the beginning of the second set," said Keys. "My energy dropped. Once I got broken in the third, I just kept telling myself, Just try to figure it out, just get as many balls in as you can."

The increasing strength of the American's returns forced Svitolina to press more, and her unforced errors became more frequent. A messy service game at 4-3, punctuated by a Keys service return winner to break for 4-4, frustrated the fourth seed, and it was an irrevocable turning point towards the match slipping out of her grasp.

By now, Keys had found her range on both sides, and more winners appeared. After Keys held easily for 5-4, more strong returning and rallying by the American was too much for Svitolina, whose first serve had completely deserted her. A backhand winner on match point completed Keys' four-game streak to win the set and the match from behind.

"I went from being down 5-0 in the second set to kind of just making a lot of balls and being tough," said Keys. "I'm really happy with how I closed out the match today."

Keys will play Estonian qualifier Kaia Kanepi in the quarterfinals, and joked that perhaps another night match would be perfect. "I mean, why not?" she told the press. "Let's just change the whole tournament. We'll start at 10 p.m. every night. Clearly I'm on that schedule already, might as well stay on it."

"I'm afraid to, like, play in the sun," laughed Keys, "because I haven't done it in two weeks."