There are surprising Masters finals, and then there’s Sock-Krajinovic; I won’t even bother asking if you had this as your Bercy final at the start of the week.

Over the last six days, the two 25-year-olds have been revelations, in very different ways. Before Bercy, the 77th-ranked Krajinovic had qualified for just one ATP-level event in 2017. This week, though, he has given us an idea of how he racked up 66 wins on the Challenger circuit. While he hasn’t beaten a Top 10 player in Paris, and he caught the break of all breaks when Rafael Nadal withdrew from their quarterfinal, Krajinovic has shown off a smoothly effective game. He appears loose and relaxed, and hits the ball cleanly from both sides; his down-the-line backhand in particular has been a thing of simple beauty. And when it came down to the crunch against John Isner in the semis, it was Krajinovic who looked like the more experienced player. At 5-5 in the deciding tiebreaker, he anticipated Isner’s first serve and rocketed back a point-winning return. And at match point, he nervelessly knocked off a forehand winner.

With Sock, the revelation hasn’t been his game; we already know how rapidly he can swing a racquet, and dash around a court. The difference this week has been how unflappable he has been, in a minimalist sort of way. The backward baseball cap is gone, as are, for the most part, the sarcastic reactions and running conversations with his team. After reaching just one semifinal since April, and recording a 3-4 record at the majors, Sock seems to be playing with nothing to lose in what he must have assumed would be his final tournament of the season.

The question is: Now that Sock knows he’ll get to play again, at the prestigious World Tour Finals in London, if he wins this match, will he continue to feel like he has nothing to lose? If not, Krajinovic looks ready to go all the way.

Winner: Sock