American 13th seed Madison Keys overcame a second-set wobble to beat Japan's Naomi Osaka 6-1 7-6 (7-5) and set up a last-16 clash with Romanian Mihaela Buzarnescu at the French Open.
A match between two of the biggest hitters on the WTA Tour failed to really catch fire on a cool and half-empty Suzanne Lenglen Court with Keys helped on her way to the first set by a succession of wild errors from Osaka.
Keys broke for a 3-1 lead in the second set and looked to be closing in on a straightforward victory when 21st seed Osaka suddenly found her range and levelled the set.
Osaka's mini-revival looked to have fizzled out when she dropped serve with a double-fault at 4-4.
Keys squandered a match point in the next game, however, and the 23-year-old US Open runner-up looked increasingly tight as the set moved into a tiebreaker.
Osaka led 4-1 but Keys dragged it back to 4-4 with a searing backhand pass but faced a set point at 5-6 and needed some superb defence to fend off the fired-up Japanese.
Keys saved another set point at 6-7, this time with a booming first serve. She then wrong-footed Osaka to bring up a second match point and was relieved as her opponent coughed up another double-fault to end the contest.
Keys will next face Buzarnescu, who later put out fourth-seeded Ukrainian Elina Svitolina 6-3 7-5 on Friday.
The 23-year-old Svitolina, who trains at Roland Garros and was a quarter-finalist in 2015 and 2017, had been tipped as one of the potential winners this year after winning the Italian Open, but she never found her groove on Court One.
She dropped serve five times and made 29 unforced errors, bowing out on the first match point when she buried another forehand into the net.
Employing a vicious topspin forehand modelled on her idol Rafael Nadal's weapon-of-choice, Russian Daria Kasatkina recovered from a mid-match blip to reach the last-16, defeating Greece's Maria Sakkari 6-1 1-6 6-3.
After reaching the fourth round for the first time, 2014 junior champion Kasatkina was quizzed about what she had learnt from French Open legend Nadal.
"A lot, a topspin forehand, movement on the court and fighting spirit for sure. Because I watched Rafa a lot, I started to spin the ball," the 21-year-old, who flashed 11 forehand winners compared to just two from her backhand, said.
Kasatkina will face either Australian Open champion Caroline Wozniacki or French wildcard Pauline Parmentier in the next round.