!Picby Pete Bodo

WIMBLEDON, England—Maria Sharapova trailed Sabine Lisicki by a set and 3-5, and was serving at 30-0. The No. 1 seed was fighting for her competitive life and barely hanging onto it against the 5-foot-10, German-born, 22-year-old. During the next point, Sharapova left a ball short and Lisicki, who trusts power over finesse by a wide margin, moved forward and carved under the ball to drop a short one just over the net—so close to the sideline that when it was called out, Lisicki issued a challenge.

While the pixels and algorithms were humming into play, Lisicki turned to her father, Richard, seated in the guest box, and pressed the pads of her thumb and index fingers together, laughing and smiling. It was atypical behavior for an underdog at a critical time in a match, but the image spoke volumes about the confidence and relaxed attitude of the swaddled-in-white challenger.

The challenge was denied. Lisicki kept smiling.

Across the net, Sharapova was Little Miss Poker Face—an entirely appropriate reaction given the straits she was in. She would go on to hold serve with the help of that oh-so-close error by Lisicki, but it only forestalled the inevitable.

Granted, Lisicki made an adventure of her next service game, squandering two match points (one via an overly enthusiastic forehand approach shot that looked to be a sure winner; the other with a similiar set-up shot drilled into the net). Still grinning and oblivious to the menacing, slate-tray overcast that had already caused one stoppage of play (after Lisicki won the first set), Lisicki calmed down and won the next three points, finishing Sharapova off with an ace.

It was as fine a display of power tennis as we've ever seen by a woman at Wimbledon, and the 6-4, 6-3 triumph confirmed that Lisicki, despite a history of injury, is not a mere sideshow (Come, see the Troisdorf Thunderer bang out 20 aces and 40 unforced errors!) but a serious contender for this title. Lisicki was spanked in the semis here last year by Sharapova, whose game is only somewhat similar. Lisicki also pushed Sharapova to three sets at the Australian Open at the start of this year, but still lost, and had yet to win a match after three meetings. Was the win today "revenge for last year," she was asked?

"Yeah. For all three times," Lisicki gayly replied.

Sharapova could only say, "A lot of the credit goes to my opponent. She played extremely well today and did many things better than I did on this given day. You just have to hand it to her."

And you know Sharapova. She doesn't like handing anyone anything.

When I caught up with Sabine's father and coach in the player tea room later, he told me, "It was already starting to come together for Sabine at Charleston, but her injury stopped her. Now I think she's ready to do it. She was focused and the last match against Maria (in Australia) was close, so we knew she could win."

Lisicki has always been recognized as a dangerous talent, if prone in her first few years on the tour to losing control of those big groundstrokes and that 120 M.P.H. serve. At just about the time her game was coming together in 2010, she injured her ankle so badly that she was off the tour for five months and finished the year ranked No. 179. Lisicki fought her way back in 2011, crowning her resurgence here in London with wins over Li Na and former finalist Marion Bartoli, before being dismissed by Sharapova.

By Charleston time this spring, Lisicki was back up to No. 13. And at that tournament she led Serena Williams, 4-1, when she rolled an ankle—again. After returning at Rome, she lost in the first round in her next four events, leading right up to the eve of Wimbledon. After the last of those losses, at Birmingham, Lisicki decided she'd had enough rain and returned to train at home in Bradenton, Fla. for a week before the start of Wimbledon. "I got my confidence and my shots back," she said of that impulsive interlude. "I had fun on the court again."

The fun she had today was at the expense of a woman who was riding a 15-match winning streak; over that same period, Lisicki was 0-4. Sharapova was 39-5 on the year going into the match, Lisicki a pale 13-13. So how did this come about?

As Sharapova said, "She's always had that potential. . . I mean, if she plays at this level, of course she belongs at the top. If she serves as well as she did today and is as aggressive as she was, there's no doubt she has a lot of potential."

Sharapova also knows that you can't dismiss Lisicki as a mere carnival act. "Well, she stays really low," Maria explained. "She's a strong girl. She hits the ball really hard. If you don't get a good first ball on her, I mean, she likes to be the aggressive one and likes to start the point with a really heavy shot."

The analysis is not just accurate, it's a foolproof template for winning at Wimbledon. The Troisdorf Thunderer knows this, which helps explain why she continued turning those highbeam-eyes and smiling face upon the world long after she'd demolished the favorite and French Open champion. (This, incidentally, is habitual with Lisicki at Wimbledon. She also bumped out Roland Garros champion Svetlana Kuznetsova in 2009 and 2011 champ Li last year).

Lisicki is rightfully proud of her serve and she makes no bones about her appetite for playing "aggressive" tennis. She feels comfortable moving on grass, a prejudice that, given her history of injury and the slick properties of the surface, can only be attributed to how good she feels in general. How happy she is to be here. "The atmosphere here at Wimbledon is just amazing," she said, wide-eyed as a first-time grounds pass holder. "You know, all the traditions make me feel very comfortable here."

Frozen grins excepted, players who are quick with a smile and manage to enjoy their experience at Wimbledon are among the most dangerous. If they gave points for attitude, Lisicki might immediately be bumped up to the favorite for the title. Her feelings are so clear and accessible that she answered just about every question put to her in the press conference with nary a qualifier, nor any of the familiar convoluted ambivalence that grips so many players. Is she going to feel more pressure now that she's in the quarterfinals?  "I don't see any pressure for myself," she said. "I just go out there, enjoy it, and want to play the best tennis I can and keep improving. Why should I put pressure on myself?"

Of course, other players have been no less sanguine about their chances, and comparably happy and confident, only to have their dream-like state shattered, like the way Lisicki's countrywoman Angelique Kerber destroyed Kim Clijsters, 6-1, 6-1, in her final hope to win Wimbledon before she retires. Kerber and Lisicki will meet in the quarterfinals, and as Richard Lisicki said, "German against German, It will not be easy."

No, but unless Lisicki undergoes an overnight transformation, it will be fun.