On the penultimate day of the ATP World Tour Finals, the top two men in the world meet two of the season’s breakthrough stars with a trip to the final at stake.

Kei Nishikori v. Novak Djokovic

The first semifinal pits the newly decorated 2014 year-end No. 1 Novak Djokovic against a fearless challenger, Kei Nishikori. Djokovic is surely the favorite entering this match, but if Nishikori is able to put his game together as he did against David Ferrer on Thursday, this may not be as one-sided as Djokovic’s other matches have been this week.

Going back to the Paris Masters, Djokovic has faced minimal resistance. He has not lost a set in eight matches and has only seen one tiebreak, which required Gael Monfils to soar to breathtaking levels in Bercy.

Nishikori has been up and down this week. He beat Andy Murray in his first round-robin match but was not anywhere near his best. Against Roger Federer, his level of play dipped even more. In his final round-robin match against David Ferrer, his streak of poor play continued until he finally turned things together when it mattered most in the final two sets.

Djokovic and Nishikori last met in Paris just two weeks ago. Similar to the situation here in London, Nishikori had just beaten Ferrer to guarantee his spot in the World Tour Finals. He comes into tomorrow’s semifinals having beaten Ferrer in his previous match to gain qualification into the semifinals. In Bercy, Nishikori was physically spent after his three-set battle with Ferrer and had nothing left in the tank against a relentless Djokovic.

Nishikori can take confidence in the fact that he has a very recent and monumental win over Djokovic that came in the semifinals of the U. S. Open back in September. 

The defensive weapons Djokovic possess seem nearly unbreakable on this slow indoor hard court. Even Nishikori, who can put the ball past anyone, will not find it easy to break down Djokovic tomorrow. It’s not an impossible mission, but it’s one that will mandate near flawless offensive execution from Nishikori.

In their U.S Open semifinal, Nishikori extracted the most value out of every point that saw Djokovic hit a short return. He was quick to get on the offensive and was particularly successful in driving his backhand cross court, coming up with acute angles and forcing Djokovic to redline his defensive efforts. The backhand-to-backhand rallies were fairly even in this match, but Nishikori was the more willing risk taker and was able to find the mark on no shortage of backhands that went up the line.

Djokovic has only lost nine games this week—an absurd number considering that he just played three of the top eight players on the planet. Combine this with Nishikori’s inconsistent performances and a very slow court and you have a recipe for a straightforward Djokovic victory.

Prediction: Djokovic in two sets

Roger Federer v. Stan Wawrinka

Next week, Stan Wawrinka and Roger Federer will be teammates fighting for the same trophy as they compete in the Davis Cup final against France. Tomorrow, they’ll only view each other as obstacles in pursuit of a spot in the final of the season-ending championships.

Entering this tournament, Wawrinka was considered to be the player least likely to win the event. With his victory over Cilic on Friday, he exceeded the amount of matches he won between the U. S. Open and the World Tour Finals, which was just one.

Federer, on the other hand, won titles in Basel and Shanghai entering this event and could not be in better form. His 6-0 6-1 win over Andy Murray on Thursday was clearly a fluke of sorts but still shows how well Federer has been playing as of late.

Just as will be the case with Nishikori, this match could end very quickly, or it could prove to be quite the affair if Wawrinka can bring his A game. Wawrinka has verified that he is able to take on and defeat any opponent thrown his way if his level is high enough. With this said, this has been a huge if for him this year, especially following the Australian Open and then Monte Carlo. In the last 15 months, Wawrinka has beaten Federer, Murray, Djokovic, and Nadal. Such a feat would have seemed unattainable a few short years ago.

For Wawrinka, winning a match like this one over Federer was almost entirely out of the question until this year. We can talk about how average Wawrinka has been for most of the year, but it’s more important to realize that this is a player who has beaten Roger Federer and one who can beat him again tomorrow if he plays his cards right.

Federer has yet to drop a set this week and will be well-rested after needing under an hour to dispose of Murray.

The blueprint for how Wawrinka should be playing tomorrow can be found in the highlights of the first set of their quarterfinal match at Wimbledon and the last two sets of their championship match at the Monte Carlo Masters. In both these instances, Wawrinka provided Federer with a large dosage of his own medicine. He established his dominance from the baseline with his serve and then proceeded to attack on shot after shot, interjecting seemingly limitless amounts of power and spin. There was really nothing for Federer to do but wait until the onslaught was over and on both these occasions, it never ended. If Wawrinka is going to win tomorrow, he’s going to have to go after Federer hard and often.

For Federer, this matchup is clearly a good one, considering he has beaten Wawrinka 14 out of the 16 times they’ve played. He’s able to gain control of the points pretty quickly with Wawrinka consistently chipping back returns and is able to keep Wawrinka out of the center of the court where he works best. The backhand-to-backhand exchanges are ones that Federer has handled well because he is able to vary the action by introducing the slice backhand, making it much harder for his countryman to drive through the ball and subsequently through the court.

It’s really tough to pick against Federer in this situation, so look for the Swiss to get through to a Sunday final with Novak Djokovic.

Prediction: Federer in two sets