German qualifier Daniel Altmaier, ranked 186th in the world, bundled out Italian seventh seed Matteo Berrettini from the French Open with a comprehensive 6-2 7-6(5) 6-4 victory on Saturday.
The 22-year-old was not even sure he would make his debut at this year's claycourt Grand Slam at Roland Garros as he was struggling with an injury and needed a go-ahead from a doctor at the last minute to take part in the qualifiers.
On Saturday, Altmaier picked up the biggest win in his nascent career on Court Philippe Chatrier by defeating the world number eight Berrettini, having also beaten Feliciano Lopez and Jan-Lennard Struff in his previous rounds.
"It's my first time on this court and playing in Paris, I'm delighted to be in the fourth round," Altmaier said in an on-court interview.
"My coach and I have been working so hard to be here, and while I've struggled with a few injuries, I am super pleased it's at Roland Garros.
"Before qualifying, I was struggling with an injury, so I wasn't sure I was going to play. I hope the crowd and the TV audience enjoyed watching, as I want to entertain."
He became the fourth man to reach the fourth round of a Grand Slam as a qualifier after Lee Hyung-Taik Lee (2000 U.S. Open), David Goffin (2012 Roland Garros) and Juan Ignacio Londero (2019 Roland Garros) also achieved the feat.
Altmaier broke the off-colour Italian's serve four times to win their first career meeting in two hours and 15 minutes.
"Pretty upset. I was really feeling bad on the court. I'm feeling bad now," said Berrettini. "Didn't play well in the big stage. It's painful. But I guess that's tennis.
"For me, I felt the conditions were pretty heavy. I tried to fight. I tried to play with what I had, but wasn't enough. I think he really deserved the win."
Altmaier hit 23 winners, many of them came from his sizzling one-handed backhand, while Berrettini's powerful game lacked control as he dished up 42 unforced errors, the last of them on match point.
In the fourth round Altmaier will meet the winner of the Spanish battle between 10th seed Roberto Bautista Agut and U.S. Open semi-finalist Pablo Carreno Busta, seeded 17th.
(Reporting by Sudipto Ganguly in Mumbai; editing by Christian Radnedge)
