Last week in Madrid, Keys saw off Strycova in straight sets, and she looked on course for another routine win when a run of four straight games helped her pocket the opening set.
However, Strycova had no intention on going quietly, clinging onto the American's coattails in the second set before pouncing on a lapse in concentration at 4-4 to break. The Czech calmly held her own serve, forcing a decider when a flashing Keys forehand found the tape.
Into the third, and Strycova continued to stay in touch, scurrying to all corners as she diligently tracked down the American's baseline onslaught. Trailing 4-3, though, the pressure finally began to take it's toll on Strycova, who ended a weary sequence of points by miscuing a half-volley to surrender serve.
With the match on her racquet, Keys made no mistake, serving out for a spot in her first semifinal of the season.
"It's difficult. I mean, her weapon is making you miss and just getting that one extra ball and things like that," Keys said. "There's obviously times I wasn't happy I was making the mistake, but I think you also have to beat her because she's going to stay on the other side and make a lot of balls.
"I think it was a balance between taking the risk and also having a big target."