Unseeded Danielle Collins battled past Tunisian Ons Jabeur 6-4, 4-6, 6-4 to reach the French Open quarter-finals for the first time.
World No 57 Collins raised her level after the opening nine games of the first set went with serve, when the American broke to edge ahead in the contest as Jabeur made an unforced error from the back of the court.
The big-hitting 26-year-old then raced to a 3-0 lead in the second set, showing the craftiness more commonly associated with her opponent to pull off a superb drop shot in the second game as Jabeur appeared to wilt on Court Philippe Chatrier.
But the Tunisian, who became the first Arab woman to reach the Roland Garros last 16 by beating eighth seed Aryna Sabalenka, regained focus to win the next five games in a row before dragging the match into a deciding set.
In complete contrast to the opener, both players traded breaks freely at the start of the decider before Collins came back from 0-40 to hold for 3-2 and staved off a late comeback attempt to seal the win.
"I felt I was in the driver's seat until 6-4, 3-0 ... she's tricky, served really well and hit some drop shots I wasn't expecting," Collins said.
"I had to try and dig it out. It broke my rhythm. I lost my way there a little bit, lost some of the shots I'd been hitting earlier and I needed to try and stay positive."
Collins takes on Australian Open champion Sofia Kenin next, after the fourth-seeded American beat Frenchwoman Fiona Ferro 2-6, 6-2, 6-1 in their last 16 encounter on Monday.
Argentina's Nadia Podoroska became the first qualifier to reach the French Open semi-finals in the women's singles draw when she downed Ukrainian third seed Elina Svitolina 6-2, 6-4.
The world No 131, on her second appearance in the main draw of a Grand Slam, emulates Belgium's Filip Dewulf, the only qualifier in either of the singles draws since tennis turned professional in 1968 to make it to the last four at Roland Garros, in 1997.
"It's a little bit difficult for me to speak after the match, thank you everybody for your support, I'm very very happy," Podoroska said on court Philippe Chatrier.
"We did a very good job with my coaches during quarantine. That's why I'm here today."
Svitolina, one of the pre-tournament favourites after winning the Strasbourg International last month, was on the back foot throughout, failing at the last-eight stage for the third time at the claycourt Grand Slam.
Podoroska next faces either Polish teenager Iga Swiatek or another qualifier, Italian Martina Trevisan.
Should Trevisan prevail in her quarter-final, it would ensure a qualifier plays in the final of a Grand Slam for the first time in the Open era.
Since 1968, only Alexandra Stevenson at Wimbledon in 1999 and Christine Dorey at the 1978 Australian Open had made it to the semi-finals at a major prior to Podoroska. Both of them failed to go one step further.
Coming into Tuesday's match, the 23-year-old Podoroska had won seven matches in a row at Roland Garros, and she kept that momentum going against Svitolina.
The Ukrainian broke her serve in the first game, but then Podoroska turned on the engine and bagged five games in a row to move to 5-1.
Having converted all of her four break points while Svitolina converted only two of six, Podoroska found herself one set up after 37 minutes.
Perfectly mixing power and a gentle touch with drop shots, Podoroska proved too skilful for Svitolina, who looked nothing like the player who reached the semi-finals at Wimbledon and the U.S. Open last year.
Six consecutive games went against serve in the second set until Podoroska held for 5-4 before wrapping it up on Svitolina's serve on her second match point with a forehand winner.