Ailing Kvitova pulls out of Paris
Petra Kvitova of the Czech Republic hits a shot on day one of the 2014 Australian Open tennis tournament in Melbourne on January 13, 2014 - by Mal Fairclough
Kvitova of the Czech Republic withdrew ahead of her second round date with France's Alize Cornet.
Cornet will now face Kvitova's compatriot, Barbora Zahlavova Strycova, 74th in the WTA rankings.
"I was absolutely intent on playing today but I had to see my doctor as I wasn't feeling well," Kvitova said.
"I've got a sore throat and after practising this morning I realised that after 10 minutes I wasn't able to breathe so unfortunately I was forced to withdraw."
Kvitova, ranked sixth in the world, won the Paris Open in 2011.
Cornet or Zahlavova Strycova will next play Germany's world number 39, Andrea Petkovic who put out France's 62nd-ranked Kristina Mladenovic, 6-4, 6-2.
Mladenovic had only returned to Paris on Monday after winning the Australian Open mixed doubles title with Canada's Daniel Nestor.
After putting in a fine performance to knock out world number 10, Simona Halep on Wednesday, she ran out of steam in the second round.
"After travelling for 30 hours,I came straight to training and my neck problems returned on Thursday," she said.
"At the start of the match,I couldn't serve and the injury limited my movement."
Meanwhile, Belgian eighth seed Kirsten Flipkens beat Austria's Yvonne Meusburger, 6-1, 6-3 and will face top seed Maria Sharapova in Friday's quarter-finals.
Ukraine's Elina Svitolina put out Galina Voskoboeva of Kazakhstan, 6-1, 6-2.
She will next face Italian third seed Sara Errani who saw off compatriot Karin Knapp, 6-4, 6-3.
Friday's fourth quarter-final sees Germany's Angelique Kerber face Russia's Anastasia Pavlyuchenkova.