Madison Keys versus Dominika Cibulkova

By the time play comes to a close on Monday, only eight women will remain in contention for the US Open crown.  Madison Keys, last year's finalist, would dearly love to be one of those eight and keep her hopes at a second crack at the title alive and kicking.  She will have her work cut out for her, however, against a feisty opponent named Dominika Cibulkova.  The Slovak is well known for her competitive spirit, relentlessly tracking down balls and fighting until the very end, no matter the score.  With her ability to hit flat, take the ball on the rise, and stay up on the baseline, she is also capable of playing a bigger and more imposing brand of tennis than her small physical stature would suggest. 

She is a former Australian Open Finalist and has gone deep at the other majors as well, so she is a competitor that everyone takes seriously.  The good news for Keys is that she has yet to drop a set to Cibulkova in their four prior meetings.  She is also in the driver's seat as far as keeping that pristine record intact.  The only area where the twenty-ninth seed holds an advantage over her is in movement, but past history suggests that when Keys is playing her A-game, that does not matter.  She has sufficient firepower to hit Cibulkova off the court, and the fourteenth seed has a decisive edge on serve.  So, while Cibulkova should not be dismissed and certainly has the credentials to garner the upset, if Keys has her game in good order, she will remain undefeated against the Slovak and move through to the quarterfinals.

Marin Cilic versus David Goffin

With so much of the focus on a potential Roger Federer/Novak Djokovic quarterfinal, it can be easy to forget that there are other players in the bottom portion of the draw, who could instead be the last man standing come next Sunday.  Among them are Marin Cilic and David Goffin, though for one of them, the dream of capturing the 2018 US Open title will come to end in the Round of 16.  As to which will advance and who will see his journey end is really anyone's guess.  The two are separated by only three places in the rankings, with Cilic the higher of the pair at Number 7.  Goffin leads this rivalry by a slight margin of 3-2, but it is the Croat who has won their two most recent encounters. 

Goffin has looked steadier to this point, but Cilic is the player who has enjoyed more success at the majors, winning the title here in 2014 and reaching the final of Wimbledon last season and the final of the Australian Open this past January.  With little to choose between the two, it comes down to execution of their respective games on the day.  Goffin must do what he does best, which is staying up on the baseline, taking the ball early, and be willing to take a few more risks by changing the direction of the ball to go up the lines to create space and force his opponent into errors.  As for Cilic, he has to remember that he is the one equipped with the superior set of weapons.  He can generate greater firepower off the ground, and he needs to have a good serving day to take full advantage of the clear edge he enjoys on serve.  If he can do that, then he will be the one who remains in the title hunt.

Naomi Osaka versus Aryna Sabalenka

The veterans may still be the ones earning most of the headlines, but youth is also being served at this year's US Open.  In a battle of the next generation, Naomi Osaka will face off against Aryna Sabalenka with a berth in the quarterfinals hanging in the balance.  The young Japanese woman really made her mark this spring when she put together a string of notable victories en route to winning her first title at Indian Wells.  Although she has struggled to balance the expectations that came with the stunning victory, she has looked great here in New York.  She has barely dropped games, let alone sets in reaching the fourth round here and will be keen to keep up her run of good form to continue her journey towards the title.  She faces a monstrous hurdle though in Aryna Sabalenka.  Like Osaka, the Belorussian is only twenty-years-old, and she has made her splash on the tour this summer.  It started on the grass in Eastbourne and continued during the US Open Series where she reached the semifinals of Cincinnati before going on to capture her first tile in New Haven. 

She has had to work harder to get to this juncture than the twentieth seed, but she has been no less impressive, particularly with the way she took two-time Wimbledon Champion Petra Kvitova out of the match in the last round.  Both women should be feeling confident as they look to go deeper here in New York, and that could prove crucial in the key moments.  If she can rise to the occasion, this match really hinges on the racket of Sabalenka more so than it does Osaka.  The Belorussian possesses more firepower from the ground and on serve, and she takes the bull by the horns in the big moments rather than shying away from them.  She is unafraid to move forward and is always regularly looking to be the one dictating play.  Osaka has a similar approach, but she cannot match the firepower of the twenty-sixth seed.  She is going to have to be the one to take a few more risk to get Sabalenka out of position or hope that the moment gets to her opponent if she wants to avoid the upset.  With so little experience playing matches of this magnitude, there is no sure way to know how either will react to it, but if Sabalenka does manage it, her game should be enough to see her through to victory.