Magda Linette came from two breaks down in the first set en route to beating No. 4 Caroline Garcia 7-6 (3), 6-4 on Monday to reach her first Grand Slam quarterfinal.
She will face Karolina Pliskova, who defeated Zhang Shuai 6-0, 6-4 in another fourth-round match on Monday.
Linette was lost for words in the on-court interview after the match.
“I don't really believe it,” she said. “I can't believe it, really. I don't know what happened. I'm speechless really. I don't know what to say.”
Fifth-seeded Aryna Sabalenka defeated Belinda Bencic 7-5, 6-2 on Monday to reach the quarterfinals for the first time. Bencic double-faulted to drop the first set, which put Sabalenka in control from that point.
“I’m super happy with the win today,” Sabalenka said. “She (Bencic) is an unbelievable player. She played so good. I’m really happy with the level today.”
Sabalenka faces Donna Vekic, who defeated Linda Fruhvirtova 6-2, 1-6, 6-3.
Two other quarterfinal matchups were already set, with Elena Rybakina facing Jelena Ostapenko, and Jessica Pegula playing Victoria Azarkena.
Top-seeded Iga Swiatek and No. 2 Ons Jabeur have been eliminated, leaving No. 3 Pegula as the highest ranked women through to the final eight.
Sabalenka said she had worked hard on controlling her emotions during matches.
“It takes me a little while to understand that negative emotions are not going to help me on court,” she said. “You just have to stay strong and believe no matter what.”
Sablenka also said her fitness has improved.
“We did a lot of work in the preseason and I'm super happy that everything is working right now,” she said.
Novak Djokovic faced Alex de Minaur Monday for a place in the men's quarterfinals. Djokovic is aiming for this 10th title at the Australian Open and his 22nd Grand Slam title. The Grand Slam mark would tie him with Rafael Nadal for the most by any man.