WATCH: Madison Keys beats Svetlana Kuznetsova to win Cincinnati

On Sunday in sweltering Cincinnati, a former US Open finalist ousted a former US Open champion to emerge from a six-match gauntlet in one of the biggest hard-court tournaments of the season.

Garbine Muguzura, Daria Kasatkina, Simona Halep, Venus Williams, Sofia Kenin, Svetlana Kuznetsova: Madison Keys beat them all to complete one of the most difficult runs I've seen in a non-Slam event; incredibly, five of those players were unseeded. Such is the possibility in a 56-player tournament with just 16 seeds—Keys being No. 16. Every player Keys beat has been ranked inside the Top 10, and after Kenin's summer, she isn't that far away.

It's hard to decide which victory this week was Keys' most impressive, but her final-round win over Kuznetsova is certainly in contention. With the pressure on her as the crowd favorite and the seeded player, Keys fell behind an early break to Kuznetsova, boasting a dangerous blend of carefree and confidence. But at 4-5, Keys began a two-break, three-game run, snagging the set to shift the tenor of this match.

Keys completed her 7-5, 7-6 (5) win in similar fashion, saving her push until the last moments of the second set with a critical break. Her serve was the difference maker, as it perhaps should be no matter where she plays. Keys fired 13 aces on the day; she has never hit more aces in a single tournament than she did this week.

While Keys may be still known more for her inconsistency than her serve, she'll have a major opportunity to change that narrative in eight days at the US Open. If she does, you can bet that her serve will play a major part—and that she may need to set another tournament record in the process.