Two-time runner-up Bethanie Mattek-Sands went by way of a second-round upset Thursday at the $235,000 Bell Challenge tennis tournament.
Young Croat Ajla Tomljanovic was leading the fourth-seeded American, 7-5, 3-6, 4-1, when Mattek-Sands retired after taking a spill on the court on the indoor carpet at PEPS on the campus of Laval University.
Mattek-Sands reached the finals here in 2008 and 2010.
Up next for Tomljanovic in the quarterfinals will be sixth-seeded Marina Erakovic, who was runner-up here two years ago.
Third-seeded Czech and 2009 Quebec runner-up Lucie Safarova avoided an upset by holding off Croat Mirjana Lucic-Baroni, 7-6 (7-4), 7-6 (12-10).
She'll next face Lauren Davis, who also had to work her way to victory. The seventh-seeded American needed three sets to dispose of Czech Andrea Hlavackova, 6-1, 2-6, 6-3.
Second-seeded Kristina Mladenovic was winning 6-3, 2-3 when opponent Petra Martic retired. In third round play, she will take on fifth seed Eugenie Bouchard, who defeated qualifier Sesil Karatantcheva, 7-6 (7-2), 6-4.
The 2013 Bell Challenge champion will earn $40,000.