Maria Sharapova, who plays Sabine Lisicki next, is well aware after Rafael Nadal's defeat that no one can be underestimated. Photograph: Facundo Arrizabalaga/EPA

Maria Sharapova is right to be wary. The world No1 might be the favourite to win her first Wimbledon title since 2004 but after Rafael Nadal's jaw-dropping defeat by Lukas Rosol, Roger Federer's dice with disaster against Julien Benneteau and the exits of Samantha Stosur, Venus Williams and Caroline Wozniacki, there is an extra air of caution in the SW19 air. "It's tennis," said Sharapova after Nadal's shock defeat. "We can never underestimate who we're going up against."

Sharapova is unlikely to make that mistake against her fourth-round opponent on Monday, Sabine Lisicki, the 22-year‑old German nicknamed "Boom Boom" because of her huge serve and thumping groundstrokes. Lisicki, the 15th seed, was perhaps the feelgood story of last year's tournament; having missed most of 2010 through injury, she regained her fitness in 2011, earned a wild card for Wimbledon and romped to the semi-final, winning the crowd's affections along the way with her unrelentingly positive attitude.

There she was beaten by the brute force of Sharapova, although Lisicki dictated much of the first set, before Boom Boom was blasted to smithereens by the Russian. If this has been a quieter tournament so far, maybe that is the way Lisicki likes it. In her second-round match against Bojana Jovanovski she complained to the umpire about her opponent's grunting. Sharapova is a serial grunter but Lisicki says she will not bring it up. For her part, Sharapova has been diplomatic on the subject.

Sharapova's year began in bitter disappointment as she lost 6-3, 6-0 to Victoria Azarenka in the final of the Australian Open, yet she came to Wimbledon having completed her career grand slam at the French Open. She is the woman to beat although, while she was largely unflustered in the first week, Sharapova is occasionally guilty of losing focus, particularly on her serve. She has hit the third most double-faults, 19. Directly above her is Lisicki with 20. It could be a wild match.

All around the draw lie players waiting to make a mockery of the assertion that this is Sharapova's tournament to lose. Petra Kvitova, who beat Sharapova in last year's final, has overcome a shaky start to live up to her status as reigning champion. The Czech is not going to give up her title without a fight and should dispense with Francesca Schiavone on Monday. Then there is Azarenka, the No2 seed who never seems to get the attention her talents deserve. She will on Monday, though, having been given Centre Court billing for her match against Ana Ivanovic, the 2008 French Open champion who has never quite dealt with the high expectations that followed her Paris triumph.

Azarenka and Kvitova are both young, with reputations to burnish and legacies to write. For Kim Clijsters, her standing in the game is beyond reproach, and having made one return from retirement, the Belgian plans to quit for good after the US Open. A first Wimbledon title would be some way to bow out but she will need all her experience today against the left‑handed No8 seed, Angelique Kerber.

Yaroslava Shvedova's reward for making Wimbledon history with her golden set against Sara Errani on Saturday is a meeting with the four-times champion Serena Williams.

There have been better prizes and Williams, who survived a scare against Jie Zheng, was not being entirely serious when she said: "Hopefully I'll be able to win a point in the set. That will be my first goal and then I'll go from there."

The perfect set is something she had never heard of before Saturday, however, let alone achieved. "I never knew that existed," Williams said. "I was like 'What does that mean'? I immediately thought 'She won all four in a row and the Olympics?' I thought that wasn't possible. That's the only golden thing I know of."

Still, even though Shvedova has the golden set, Sharapova remains the golden girl – for now.