Jennifer Brady set up an Australian Open quarter-final meeting with her fellow American Jessica Pegula with a 6-1, 7-5 win over Donna Vekic.
Brady began the match at breakneck speed, racing into a 5-0 lead in next to no time.
Vekic spared herself a bagel with a gritty hold and made her opponent wait to seal the first set, saving four set points, but a volley of unforced errors and double faults had her facing an uphill battle from the early stages onwards.
Vekic had started the match with her right leg heavily bandaged and she needed lengthy treatment at the start of the second.
Either the extra strapping or the painkillers freed her and she was able to fight much harder in the second, breaking back instantly when Brady burst through her defence.
But a double fault handed the American a chance to serve it out and she did not refuse it.
"Super excited to be in the quarter-finals," Brady said afterwards.
"That was a really tough match. I had to stay focused in the second set. I was getting a little ahead of myself but I was able to break and serve probably my best game at the end.
Highlights: Brady battles past Vekic to reach quarter-finals
"In the first set I came out really strong, wasn't making many errors. She was giving me a few free points here and there and I was taking advantage of that.
"In the second set, she stepped up and started playing better."
Brady was forced to spend the period before the tournament in hotel quarantine and opened up on the experience.
"Before I even came to Australia, I was actually googling people's experiences in hard lockdown because I told myself, 'I don't think I can do it'.
"Luckily the Australian Open was right around the corner so there was something to keep me motivated to train, to keep my fitness levels up and I got through it."
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