Kaia Kanepi surprised even herself by holding her nerve to eliminate second seed Aryna Sabalenka in a final-set tie-break and reach Australian Open quarter-finals for the first time.
The world number 115 edged a topsy-turvy battle 5-7 6-2 7-6 (10-7) on Margaret Court Arena to set up a meeting with Iga Swiatek in the final eight.
With Monday's impressive comeback win, Kanepi has now completed a clean sweep of reaching the quarter-finals of all four majors, making her the 15th active player to do so.
But after squandering four match points in the 10th game of the deciding set, Kanepi admits she struggled to keep her nerves in check when the match went the distance.
"I thought I was going to lose it after the match points I had on my serve," said the 36-year-old, who finished with 30 winners and 30 unforced errors.
"It was really difficult to come back. I don't know how I managed to do it.
"I was really tight. My hand was shaking when I started serving. I didn't make any first serves in, and that added to the pressure.
"It was quite crazy. I think I would be more happy if I won after two, three match points. It was really close that I lost the match. I feel a bit exhausted right now.
"The Australian Open was the only quarter-final grand slam I was missing. Given my age, I didn't actually believe I was going to do it. I'm really happy."
After sealing a 14th career victory over a top-10 opponent, with her second win in a row against Sabalenka, Kanepi is now relishing Wednesday's battle with Swiatek.
That will pit the youngest and oldest remaining players left in the draw against each other, with 20-year-old Swiatek having earlier defeated Sorana Cirstea in three sets.
"I haven't watched her, I never played her, and I don't know how her ball feels, so we'll see when I play her," Kanepi said of her next opponent. "What I expect is to play good."
Kanepi is one of six Australian Open quarter-final debutants remaining, with top seed Ash Barty and Madison Keys the only two to have previously reached this stage.