Saturday 13 September 2014 19:50, UK
Top seed seed Venus Williams was taken the distance but booked her place in the Coupe Banque Nationale semi-finals.
The American world number 19 won the first set of her last-eight encounter against Lucie Hradecka 6-3 before the Czech hit back to win the second 6-4.
However, Williams - a seven-time grand slam singles champion - kept her composure when the decider went to a tie-break and wrapped up a 6-3 4-6 7-6 (7-3) victory in two hours and 10 minutes.
Williams will face fellow American Shelby Rogers later on Saturday for a place in the final after the fourth seed ended the challenge of Germany's Tatjana Maria with a 6-4 6-2 victory.
"She (Hradecka) really goes for everything. In the end defence helped me a lot," Williams told wtatennis.com. "She hits as hard as she can and just goes for it.
"If she can keep that level up she should be more or less at the top of the rankings. But I'm happy I was able to get those last few points to go my way tonight.
"It was so difficult to beat her though. It was a beautiful performance from her."
