Jessica Pegula crashed out of the Madrid Open following a straight-sets defeat by world number 56 Moyuka Uchijima.
The Japanese took just one hour and 20 minutes to prevail 6-3 6-2 and record her first career top-10 victory.
A recent winner in Charleston, Pegula came into the contest with seven wins from eight matches on clay this year, while she was seeking a tour-high 28th win of the season.
However, the world number three was broken five times by Uchijima, who also saved five of seven break points on the way to setting up a last-16 clash with either Daria Kasatkina or Ekaterina Alexandrova.
Jasmine Paolini was another big name to fall in the Spanish capital on Sunday; the two-time major runner-up going down 6-2 6-1 against Maria Sakkari.
The former top-10 player and French Open semi-finalist had slipped to 82nd in the WTA rankings following a difficult season.
However, Sakkari fired six unanswered aces, and broke her opponent six times on the way to securing a last-16 showdown with either Elena Rybakina or Elina Svitolina.
The Greek is into the round of 16 at a WTA 1000 event for the first time since last year's Italian Open, and will be joined by Anastasia Potapova after she defeated former Australian Open champion Sofia Kenin 3-6 6-4 7-6 (8-6).
18 - At WTA-1000 events since 2020, only four players have claimed more wins over WTA-1000 champions than Maria Sakkari (15) – Iga Swiatek (35), Aryna Sabalenka (24), Jessica Pegula (20) and Elena Rybakina (18). Level.#MMOPEN | @MutuaMadridOpen @WTA @WTA_insider pic.twitter.com/cCk5BP9p2P
— OptaAce (@OptaAce) April 27, 2025
Data Debrief: Uchijima achieves personal best as Sakkari stops streak
Uchijima registered the biggest win of her career to date. Indeed, it was her first victory over a top-10 opponent, having lost each of her first six such matches.
Meanwhile, Sakkari showed signs of her old form by ending her eight-match losing streak against top-10 opponents.
The Greek did so in fine fashion, too, conceding just three games; the fewest in her career on the way to such a victory.