The Cincinnati Open has seen its fair share of shocks and surprises already.
Alejandro Davidovich Fokina retired from his match against Joao Fonseca despite leading the contest, Daniil Medvedev was stunned by Adam Walton, and Washington Open champion Leylah Fernandez was beaten by Jessica Bouzas Maneiro in the second round.
Many of the usual names remain, with the likes of Coco Gauff, Carlos Alcaraz and Aryna Sabalenka all advancing to the fourth round.
However, there has been one player, ranked outside the top 100 on the WTA Tour, who has knocked out two top 30 players on her way to the fourth round: Emma Navarro and McCartney Kessler.

This player, who has reached her first WTA 1000 fourth round, faces an unseeded opponent in her next match; opening the door to a shock quarter-final appearance in Cincinnati.
Meet Ella Seidel
Ella Seidel was far from expected to make significant inroads at the Cincinnati Open. After all, the 20-year-old is ranked 109 in the world.
The German star had to win two qualifying rounds to play in the main draw. After doing so, she defeated Polina Kudermetova in the first round of the main draw, winning 1-6 6-3 6-2.
Seidel then stunned world number 11 Emma Navarro, winning their contest 6-4 1-6 6-4.
She followed this up by defeating Nottingham Open champion McCartney Kessler in the third round, winning an extremely close contest 6-4 2-6 7-6.

Seidel, born in Hamburg, Germany, made her WTA doubles main draw debut at the 2022 Hamburg Open, before making her WTA singles main draw debut at the same tournament in 2023.
In 2024, she made her Grand Slam singles main draw debut at the 2024 Australian Open, losing to Aryna Sabalenka in the first round.
The 20-year-old reached her first two WTA Tour quarter-finals in 2024 at the Budapest Open and Prague Open.
Seidel has recorded her first-ever WTA 1000 victories at the Cincinnati Open this week, and she has an excellent opportunity to reach the quarter-final stage.
Ella Seidel faces a fellow unseeded player in the Cincinnati Open fourth round
Before the tournament, Ella Seidel may have expected to face a seeded player if she managed to reach the fourth round.
However, Seidel has been drawn against a fellow unseeded player: France’s Varvara Gracheva.
Like Seidel, Gracheva has performed impressively in Cincinnati. She has defeated two seeds on her way to the last 16: 2020 Australian Open Ladies Singles champion Sofia Kenin and 11th seed Karolina Muchova.
Seidel and Gracheva, who is ranked 103, have never met before in a match on the WTA Tour.