NEW YORK – For those hoping to see Caroline Wozniacki in vintage form this week in Flushing Meadows, they got their wish and then some.

After working her way through the first three rounds of the US Open, Wozniacki entered Sunday's action facing her biggest test in No. 8 Madison Keys.

A native of Rock Island, Illinois, Keys has come into her own over the last couple of years and, being just 21, is only at the beginning of her career. So far, though, her best finish at a Grand Slam was a quarterfinal appearance at Wimbledon in 2015. But, being ranked eighth in the world, the American powerhouse had everything working in her favor entering the fourth-round.

Being a former world No. 1, though, Wozniacki knew what it takes to shine on the biggest stage and, on Sunday, she proved just that as she made the most of her first-ever meeting against Keys.

In a match that lasted just 77 minutes, the Danish veteran fought valiantly while letting her expertise and counter-punching style do most of the talking, ousting Keys 6-3, 6-4, to advance to the quarterfinals.

Despite the loss, Keys looked strong for much of the day. She was superior in aces and winners but did commit a total of 33 unforced errors. Wozniacki committed just seven, played solid defense and, looked calm and composed from start to finish. Her 80 percent win percentage on her first serve certainly didn't help Keys' case, either.

Through four rounds, Wozniacki has lost just one set – 3-6 to American Taylor Townsend in the first round – but has not looked back since. It has been so far, so good for the Dane who has ousted two Top 10 players – No. 10 Svetlana Kuznetsova being the other – this week to reach the quarterfinals at the US Open.

In the quarterfinals, Wozniacki will face Latvian Anastasija Sevastova who made some noise of her own coming this far – her first career Grand Slam quarterfinal – as she ousted No. 13 Johanna Konta in the fourth round.

Sevastova, ranked No. 48 in the world, has faced Wozniacki just once before, losing 6-3, 6-4 in the Round of 16 at the 2011 Australian Open.

On the men's side, one compelling matchup saw No. 11 Jo-Wilfried Tsonga meet No. 27 seed Jack Sock with a spot in the quarters on the line.

In their only meeting, Tsonga came out victorious, defeating the American in the Round of 32 at the 2015 Madrid Masters.

On Sunday, Tsonga won again but needed a fight to take down Sock, defeating him 6-3, 6-3, 6-7(7), 6-2 to advance to his second straight US Open quarterfinal.

The 23-year-old American was resilient on this day, staving off elimination in the third set. In the end, though, Sock just didn't have enough to come back as Tsonga, with the help of 11 aces, 54 winners and winning 83 percent of his first serves, vaulted himself into the Round of 8 in the Big Apple. In fact, if Tsonga wins his quarterfinal matchup, he will put himself into his first Grand Slam semifinal since the 2015 French Open.

However, If Tsonga wants to advance to the semis, he must get past No. 1 Novak Djokovic, who continues to have a strong 2016.

Tsonga and Djokovic will meet for the 22nd time in the quarters with the top-seeded Serbian winning 15 times. We will see if Tsonga has what it takes to get past the one they call “Joker”.