Svetlana Kuznetsova edged into the quarter-finals of the Porsche Tennis Grand Prix with a 6-4 6-7 (5-7) 6-3 victory over Agnieszka Radwanska of Poland.
The second-seeded Russian served well against Radwanska, who was coming off a surprising win against Marion Bartoli.
The Russian fired 16 aces and saved all but one of seven break points en route to beating the Polish player for the third time - all this season.
Kuznetsova's next opponent will be sixth seed Serena Williams, a 7-5 6-2 winner over Julia Vakulenko of the Ukraine.
This is the first action since the US Open for Williams, who is making a rare appearance on the autumn swing through Europe in order to try and qualify for the year-ending WTA Tour Championships in Madrid in November.
Williams had 10 aces against no double faults and managed six breaks in facing the 24-year-old Vakulenko for the first time.
In the only other scheduled second-round match, fourth seed Anna Chakvetadze was upset by Tatiana Golovin of France 7-6 (7-3) 6-1.
It was a second straight early exit for the Russian, who was bounced from the quarter-finals of the Fortis Championships by Bartoli last week.
Golovin had six aces and five breaks as she avenged a 6-1 6-3 loss to Chakvetadze at Miami in April and grabbed a 3-2 edge in the all-time series.
In the first round, fifth seed Ana Ivanovic carried over the momentum from Sunday's win at the Fortis Championships with a 6-0 6-2 rout of Patty Schnyder of Switzerland.
The 19-year-old Serbian, who captured her third title of the year in Luxembourg, cut her deficit in the career series with the Swiss player to 4-3 and has won the last three matches dating back to 2006.
Eighth seed Daniela Hantuchova strolled into the second round with a 6-1 6-3 victory over Lucie Safarova of the Czech Republic.
The Slovakian set up a match-up with Russian Elena Dementieva, who topped Amelie Mauresmo in straight sets on Tuesday.
Dutch player Michaella Krajicek also cruised into the second round by dispatching Alona Bondarenko of the Ukraine 6-3 6-2.
Krajicek's next opponent will be seventh seed Nadia Petrova, the defending champion of this Tier II hard court event.
Also Wednesday, Kateryna Bondarenko captured a 7-5 6-0 victory over Karin Knapp of Italy.
Meanwhile, at the Tashkent Open, top seed Victoria Azarenka from Belarus scored a comfortable opening-round win over Chinese Taipei's Hsieh Su-Wei 6-3 6-4 but second seed Dominika Cibulkova from Slovakia was bundled out by Frenchwoman Pauline Parmentier 6-2 6-2.
Porsche Tennis Grand Prix, Stuttgart, Germany
Singles - First Round
5-Anna Ivanovic (Serbia) bt Patty Schnyder (Switzerland) 6-0 6-2
6-Daniela Hantuchova (Slovakia) bt Lucie Safarova (Czech Republic) 6-1 6-3
Michaella Krajicek (Netherlands) bt Alona Bondarenko (Ukraine) 6-3 6-2
Kateryna Bondarenko (Ukraine) bt Karin Knapp (Italy) 7-5 6-0
Singles - Second Round
2-Svetlana Kuznetsova (Russia) bt Agnieszka Radwanska (Poland) 6-4 6-7 (5-7) 6-3
Tatiana Golovin (France) bt 4-Anna Chakvetadze (Russia) 7-6 (7-3) 6-1
Tashkent Open, Uzbekistan
Singles - First Round
1-Victoria Azarenka (Belarus) bt Hsieh Su-Wei (Chinese Taipei) 6-3 6-4
Pauline Parmentier (France) bt 2-Dominika Cibulkova (Slovakia) 6-2 6-2
4-Elena Vesnina (Russia) bt Tatiana Poutchek (Belarus) 7-5 6-4
5-Ioana Raluca Olaru (Romania) bt Mariya Koryttseva (Ukraine) 6-2 6-2
Akgul Amanmuradova (Uzbekistan) bt 7-Olga Poutchkova (Russia) 6-3 6-4
Anastasiya Yakimova (Belarus) bt 8-Anastasia Rodionova (Russia) 6-3 6-0
Ksenia Palkina (Kyrgyzstan) bt Vlada Ekshibarova (Uzbekistan) 7-5 5-7 7-5