Atmane, ranked 136th in the world, followed up his victory over world number four Taylor Fritz with a confident performance against Denmark’s Rune to book a semi-final clash with world number one and defending champion Jannik Sinner.
“I don’t think any words can describe how I feel right now,” said the 23-year-old, adding that he had trouble sleeping after his big win over Fritz on Wednesday.
“I was just trying to be myself on the court.”
Atmane, 23, is through to his first career Masters 1000 semi-final. He is the first qualifier to reach the Cincinnati last four in 10 years.
The Frenchman had won just one of four tour-level matches this year before arriving in Cincinnati.
In an earlier match, American Ben Shelton continued his strong run with a 6-4, 6-4 win over 22nd seed Jiri Lehecka of the Czech Republic to advance to the quarter-finals.
It was a clutch performance for fifth-seeded Shelton, who was deadlocked at 4-4 in each of the two sets against Lehecka before breaking him each time and then serving to clinch the set.
Shelton will face No 3 seed Alexander Zverev of Germany in a quarter-final matchup between two players who have yet dropped a set in the event. (AFP/Reuters)