Russian second-seed Vera Zvonareva struggled to beat Fed Cup team-mate Anastasia Pavlyuchenkova to book her place in the last eight at Stuttgart's WTA tournament on Wednesday.
The 26-year-old Zvonareva, ranked third in the world, recovered from losing the first set to seal a 3-6, 6-4, 6-2 win over Pavlyuchenkova, 19, who was also part of the Russian team which white-washed champions Italy 5-0 in Moscow last weekend.
Zvonareva admitted it was no surprise to lose the opening set as she struggled to cope with her first appearance of the year on clay.
She increased her confidence as the two hour-long match wore on before blasting down three aces in the third set.
Zvonareva now faces Australia's Samantha Stosur or Daniela Hantuckova in Thursday's quarter-finals.
"She's good, we'll be seeing more of her in the future," said Zvonareva of her teenage opponent, who is on the verge of breaking into the world's top 20.
"It was my first game on clay this season, so I just hung in there.
"Last week I was practising with her a lot, but it is totally different in a match situation.
"It was hard to go out and play her, but it's part of the job."
The Russian said she is looking forward to getting in some clay-court practise here ahead of next month's French Open.
"I have been injured for the last couple of clay-court seasons, I know I can play well on the surface, I just need to get some practise in," she said.
There was a shock here as French eighth-seed Marion Bartoli was beaten in straight sets 6-4, 6-2 by German wild-card Kristina Barrios in just 85 minutes.
The German brushed off her ranking of 79th in the world to blast four aces down at her French opponent, who hit four double faults.
Barrios faces either third-seed Italian Francesca Schiavone or Poland's Agnieszka Radwanska, who meet later, in the quarter-finals.