WIMBLEDON, England—There was something different about Sabine Lisicki on Monday. I’m not talking about the fact that she pulled off one of the shockers of the fortnight and beat Serena Williams for the first time in her career. I’m talking about how she looked and sounded afterward. Yes, there were the tears and the wide smile we’ve come to know from her past upsets here. But there was also, as she sat up high and straight in front of the microphone in the interview room, a resolve—an aggressive resolve—in her eyes that I don’t think I had seen from her before. The German surprised some reporters by saying that she had never given up hope against Serena. When she was asked if she might have a let down in the next round, as so many of tennis' upset artists do, Lisicki cut him off. “I’ll be ready for tomorrow,” she said brusquely.

Words are one thing, of course, and actions another, but Lisicki walked it like she talked it today. She was obviously ready for her next opponent, Kaia Kanepi, as well as the added pressure of being the new favorite to win the tournament in many people’s eyes. Lisicki set the tone in Kanepi’s long opening service game by holding off multiple game points and breaking on her first chance. Lisicki wouldn’t face a break point as she ran out the first set from there, 6-3. She won comprehensively—with her serve, which was routinely in the 110-M.P.H. range; with her ground strokes, which pinned Kanepi back; and with her drop shot, which she used judiciously, whenever she had the advantage in a point.

We’ve seen the high-quality side of Sabine’s game in the past, of course; what was different today was that its darker, can’t-hit-the-broad-side-of-a-barn alter ego never made its customary mid-match appearance. To be fair, Bad Sabine did try to get in the on the action; there were a couple of moments when Lisicki appeared ready to head south. Serving at 4-3 in the first set, she made two straight wild errors to go down 15-30, and then hit an even wilder first serve that landed near the baseline. But she held firm on the next rally, followed that with a backhand winner, and hit a second serve ace to hold. The crisis had passed.

Another one came so0n enough, with Lisicki serving at 1-1 in the second set. She double-faulted for 0-40 and eventually was broken. But when she walked out after the next changeover, Lisicki, chewing on something, shook her head as if to say, “That’s not happening, not today." She broke back right away, and grew stronger from there. Lisicki kept the pressure on with her ground strokes, which she hit with an economical conviction, and kept finishing rallies with drop shots. By the latter half of the second set, Kanepi, playing fast and loose and sloppy, was clearly discouraged. She had never had a lead, and had only generated two break points. Lisicki finished her 6-3, 6-3 win with a Federer-esque exclamation point: A swinging forehand volley winner.

This stopper, unlike her male counterparts here, wasn’t going to be stopped. Lisicki advances to her second Wimbledon semifinal, where she’ll play the winner of Li Na and Agnieszka Radwanska. I’m guessing she’ll be ready for either of them.

!IBM Stat of the Match: Lisicki's serve was the weapon it needed to be against Kanepi; the German won 79 percent of her first-serve points.

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