Saint Petersburg - Romanian top seed Simona Halep advanced into the St Petersburg quarter-finals with a straight-sets win over Croatia's Ana Konjuh on Wednesday.
Fourth-ranked Halep crashed out of last month's Australian Open in the first round and had to rally from behind in both sets in Russia before overcoming Croatian teenager Konjuh 6-4, 7-6 (7/2).
"It was a tough match as Ana is playing very strong," said Halep, who cited her struggles with a sore knee after falling at the first hurdle in Melbourne for the second year in a row.
"I'm happy I could win this match. It was really important for me after the Australian Open. Now I feel fit and ready to play further.
"I want go to as far as possible here but right now I'm focused on my next match. It will be a tough one as the public will likely support my opponent but hopefully I will manage to win again."
Halep will next come up against Russian wildcard Natalia Vikhlyantseva, 19, who upset her eighth-seeded compatriot Daria Kasatkina 7-6 (7/4), 6-2.
Saint Petersburg-born Svetlana Kuznetsova, seeded third, also claimed a quarter-final spot by beating Daria Gavrilova 6-1, 6-3 in a replay of last year's Kremlin Cup final.
"I was a bit nervous at the beginning as I haven't played at home since I was 14," she said.
"I want to perform as good as I can and just to enjoy playing here."
Russia's Elena Vesnina and Ekaterina Makarova, who teamed up to claim doubles gold at the 2016 Olympics, faced off against each other in their opening round match.
Fifth seed Vesnina swept to a convincing 6-3, 6-1 victory to set up a meeting with Frenchwoman Alize Cornet.
"For me it's especially hard to oppose Katya (Makarova), my teammate in doubles," Vesnina said.
"We're friends, we practise together, we spend plenty of time together and it's not easy to play against her. But I'm pleased with my performance today and hopefully will show the same quality tennis in my next match here."