Novak Djokovic versus John Millman

This is not the quarterfinal folks have had penciled in or been buzzing about since the draw was announced.  It was supposed to be another marquee showdown between Roger Federer and Novak Djokovic, but a red-hot John Millman upset the apple cart by sending Federer packing and will be looking to replicate that feat by doing the same to Djokovic.  The veteran journeyman, ranked just outside of the Top 50, will certainly be game.  He competes well, and as demonstrated on Monday night, when at his best has a game that can trouble his opponents.  He can generate a lot of pace from the back of the court and from anywhere on the court, and he will unabashedly go for his shots.  He is cool under pressure on the pass, and he has a decent serve.  If he can once again get his game firing on all cylinders, he is in with a fighting chance, as Djokovic has shown himself to be vulnerable to consistent pace throughout this season. 

That said, Djokovic is still a huge favorite in this match.  His return is superior, and his groundstrokes tend to be more consistently accurate when opening up the court.  Furthermore, if he commits to staying up on the baseline and dictating points, he will not be as vulnerable to the Australian's pace of shot, as it will be harder for Millman to produce it.  Djokovic's form has also improved with each passing round, and while much of it had to do with Millman's play, there is no denying he got a fair amount of help from Federer in his upset win over the Swiss.  Djokovic looked to be in a generous mood at the outset, but he has cleaned up his game with each subsequent round and is unlikely to spray as many unforced errors in Wednesday's match.  Lastly, Djokovic does have far more experience at this level and soundly defeated the Australian when they met earlier this summer on the grass at Queen's Club, so there is every reason to expect he can repeat that result.  In short, barring another performance of a lifetime or some help from the Serb, Djokovic should avoid the Millman upset and safely move through to the semifinals.

Marin Cilic versus Kei Nishikori

In a rematch of the 2014 US Open Final, Marin Cilic will take on Kei Nishikori.  A championship crown will not be on the line, but an opportunity to move within two steps will.  Coming into this event, Marin Cilic was considered a dark horse by some and for good reason.  He is a former champion here and has been to the finals of both Wimbledon and the Australian Open, the latter coming this past January.  He has an innate offensive mindset, unafraid to pull the trigger from anywhere on the court.  His backhand is steadier off the ground, but his forehand is just as flat and dangerous.  Furthermore, he moves exceptionally well for 6'6”, and the height is definitely going to give him an edge on serve.  All of this said, the pundits are not looking past Nishikori, and some are looking to him to cause the upset. 

He does have a winning head-to-head against the Croat at 8-6, and he has been playing at a higher and more efficient level throughout this event.  He is extremely speedy about the court, and with his ability to really flatten out his shots can flick winners from just about anywhere in the court.  His backhand down the line has been particularly impressive throughout this tournament, and he will need it to be at its best come Wednesday if he wants to open up the court and take it to the seventh seed.  All told, this really has a 50-50 feel to it.  Nishikori has clearly enjoyed the better of this rivalry and appears to be in better form.  Still, it is hard to bet against Cilic.  He has defeated the man from Japan the two times they met at the US Open, and his more powerful weaponry puts him in the driver's seat as far as influencing the final outcome.  If he brings his best, he advances to the semifinals.

Madison Keys versus Carla Suarez Navarro

This probably was not the quarterfinal most were predicting, but nonetheless, it could be very compelling.  Home favorite Madison Keys has held her nerve well as she attempts to defend her finalist finish of a year ago and keep her hopes of a first major title alive.  She has dropped only one set in getting to this juncture and looked to be striking the ball very well in the previous round.  She faces a tricky prospect, however in Carla Suarez Navarro.  The Spaniard is a former member of the Top 10 and came into this event hot on the heels of a finalist appearance in New Haven.  She has been forced to put in the hard yards here in New York, but she put forth an impressive effort to defeat Maria Sharapova in straight sets in the previous round and will be keen to produce that same level against Keys.  Suarez Navarro has a beautiful one-handed backhand that she can use to throw in some slice, open up the court with acute angles, and drive it up the line. 

It is going to be crucial to employ all of those shots to keep Keys off balance.  She also packs a bigger punch than her size would suggest, and much as she did against Sharapova, she has to be willing to go after her forehand and play close to the lines.  She has pushed the American to three sets in all three of her losses to Keys, but she could finally turn the tables if she uses all of the tools in her bag of tricks.  Of course, Keys will be looking to deny the thirtieth seed the opportunity to do just that.  She boasts more firepower, and if at her best, can take the racket out of the Spaniard's hands.  Additionally, she should be able to earn a lot more free points on her serve, which should free her up on the return.  Lastly, she has to remember in the big moments that she has a perfect record against Suarez Navarro, and that she is the one who has been here before.  Evidence points to this one being a tight one, but the end result rests primarily on the shoulders of Keys.