As the last four men’s quarterfinal matchups are set, one of the game’s rising stars faces one of its most tenacious veterans. World No. 1 Novak Djokovic also eyes an unexpected challenger.

Kei Nishikori v. David Ferrer

David Ferrer probably had continuous nightmares of Kei Nishikori following the 2014 tennis season. The Japanese No. 1 beat Ferrer four times in 2014 with all four matches going three sets. Nishikori was certainly the better player at the World Tour Finals and Madrid, but Ferrer should have won in Paris Bercy and Miami. In Bercy, Ferrer was two points away from winning in the second-set tiebreak, and in Miami, Ferrer held four match points before losing in a third-set tiebreak.

The matches these two play are always of the highest quality, both physically and tactically. The rallies are grueling, lengthy, and entertaining. We see the upper reaches of offensive and defensive capabilities on a tennis court and get to witness one of the game’s great defenders take on one of its best attackers.

Nishikori and Ferrer haven’t glided through to the fourth round, with each having been forced to come back from a set down twice this event. Ferrer blew a 5-1 lead in the fourth set of his third-round match against Gilles Simon but was ultimately able to extract revenge from their third-round match at last year’s U. S. Open by winning a tiebreak.

Nishikori is the slight favorite, but this match could really go either way if both players bring their A games. A lot of people have expressed concerned for Ferrer’s level of fitness after his battle with Simon in the fourth round. We have to remember this is no ordinary player, but this is David Ferrer we are talking about.

The one thing really holding Ferrer back in this head-to-head, besides being unable to close matches, is his serve. Nishikori can attack his first and second serves with great effectiveness, making it tough for Ferrer to serve out sets and close the deal in tiebreaks.

Nishikori has had Ferrer’s number over the last year, but if this match is anything short of epic, I’d be surprised.

Prediction: Nishikori in four sets

Novak Djokovic v. Gilles Muller

On paper, this match looks like a complete mismatch. Gilles Muller is one of the best modern serve and volleyers, while Novak Djokovic is one of, if not, the best returner in the entire game. One would expect that Djokovic would be all over Muller’s serve, forcing him to produce more difficult volleys than he is used to executing.

While this may be true, Djokovic will be under severe scrutiny off his return and will have to overcome the pressure of Muller’s powerful and crafty serve while attempting to somehow bypass the large target moving towards the net.

This is the first meeting between the man from Luxembourg and the world No. 1. Muller has only dropped one set the entire tournament, beating Roberto Bautista Agut and John Isner with relatively few issues. Djokovic has been unsurprisingly dominant and has not dropped a set the entire tournament.

Muller will take a bit of confidence in the fact that he has won all six tiebreaks he’s contested this week. A tiebreak or two may be in the cards for this one, and if Muller can find himself on the offensive after the first volley often enough, he’ll definitely put the onus on Djokovic to defend, pass, and come up with the goods in the big moments.

With all of this in mind, the fact that Djokovic will have a much easier time defending his own serve despite possessing a considerably less dangerous delivery should allow him to get through this match.

Prediction: Djokovic in four sets