But the No.7-seeded Keys ended the Czech qualifier's surprise run, holding very strong on serve - she held all nine of her service games, fighting off the only break point she faced - and coming through on the return too, breaking three times. The WTA Rising Star closed it out in 67 minutes, 6-1, 6-4.
"I was just going out and trying to focus on my game, and I knew what I was trying to do," Keys said.
"It's always great when you can get off to a good start, and after that I just kept going with it. I was happy with how I stayed in the crosscourt rallies - that was definitely my biggest thing, staying in the rally and then changing direction on the right ball, then moving forward and taking time away."
Keys was asked why she didn't like just staying in the crosscourt rally and waiting for the error.
"Because that would be far too boring, and the unforced errors that come when you change down the line on dumb balls are way more fun," Keys said. "I've learned that I can play a consistent game but still be aggressive - you know, not rushing things, but also not completely changing into a clay courter."
Keys is now through to the second WTA final of her young career, her first coming at another Premier-level event at Eastbourne last year (where she edged Angelique Kerber for her first WTA title).
"I mean, it's definitely kind of surprising," Keys commented. "I don't think the grass court final surprised people as much. I just think I've made a pretty good transition from hardcourt to clay courts. And I hope I can just keep this up and continue on, no matter how I do here, to the red clay court season."
The World No.20 is also set to surpass her previous career-high of No.18 now, jumping to No.17.
Hradecka was playing her second Premier semifinal - she was a semifinalist at Madrid in 2012 too.
? WTA (@WTA) April 11, 2015