ST. PETERSBURG, Russia (AP) Tomas Berdych had to dig deep to reach the quarterfinals of the St. Petersburg Open on Thursday as he beat Andrey Kuznetsov in a deciding-set tiebreak.
The world No. 9, seeded third, struggled to return serves as he battled to a 6-3, 2-6, 7-6 (4) win over Kuznetsov, the top-ranked Russian at 46th.
Berdych next plays Italian Paolo Lorenzi, who saw off French qualifier Alexandre Sidorenko 7-6 (6), 6-4 in their second-round encounter.
Earlier, seventh-seeded Viktor Troicki beat fellow Serbian Dusan Lajovic 6-4, 6-4 to set up a quarterfinal meeting with U.S. Open champion Stan Wawrinka.
Portugal's eighth-seeded Joao Sousa also reached the quarterfinals, beating 18-year-old Russian wild card Andrey Rublev 7-6 (3), 3-6, 6-3.