In 2013, Serena Williams followed her Miami title run with another triumph on the green clay of Charleston.  She could not repeat the feat in 2014, falling in the opening round of her title defense there.

Whereas she had dominated the later rounds of Miami behind her serve, Serena gained little from her greatest weapon on Tuesday.  The world No. 1 dropped serve five times and struck just four aces to go with three double faults.  Rarely does Serena win barely half of her service points, and just 56% of her first-serve points, as was the case in her loss to Jana Cepelova.

To her credit, Cepelova did all that she could to shield her greatest weakness:  a vulnerable second serve.  The 78th-ranked Slovak maintained a first-serve percentage over 80% and saved five of the eight break points on her serve.  She served out the match with impressive composure, considering that it marked by far the greatest win of her career.

The 20-year-old Cepelova had won just 18 WTA main-draw matches in singles before this week and never has advanced past the quarterfinals at any tournament.  She did defeat former US Open champion Samantha Stosur in Doha last month, but Serena marks a giant leap above the slumping Aussie.  Cepelova now faces the challenge of refocusing from her stunning upset to exploit a suddenly open section of the draw.

Not since early 1997, when she was 15, had Serena lost an opening-round match on American soil other than by retirement.  Fatigue and a shift in surfaces must have played a key role in the result, although it does not depart too starkly from her rollercoaster start to the season.  The world No. 1 has won two Premier titles in Brisbane and Miami but also suffered a trio of puzzling losses to Ana Ivanovic at the Australian Open, Alize Cornet in Dubai, and now Cepelova in Charleston.  

But Tuesday brought good news for the Williams family as well, despite Serena's disappointment.  Earlier in the afternoon, Venus Williams weathered a three-set battle with the feisty Barbora Zahlavova Strycova.  The seven-time major champion dropped a 6-0 set for the first time in nearly four years, yet she did just enough to close out the Czech in a 7-5 final set.  Unable to serve out the match at 5-4, having held match points, Venus showed the poise of a champion in regrouping to break Zahlavova Strycova again.  She converted her second chance to close out the victory comfortably. 

Up next for Venus is a fascinating clash with Canadian teenager Eugenie Bouchard.  When they met in Tokyo last fall, Venus needed three sets to outlast the fast-rising Bouchard, who reached the Australian Open semifinals in January.  Having dropped just two games in her victory on Tuesday, the young Canadian will enter that matchup brimming with confidence.  

In fact, many women should view the rest of their week in Charleston as a golden opportunity.  From second seed Jelena Jankovic to former champions Samantha Stosur and Sabine Lisicki, an array of talented women can target the title in Serena's absence.  The tournament lost something in star power on Tuesday, but it might have gained something in intrigue.