Moscow - Top-seeded Janko Tipsarevic of Serbia advanced to the quarter-finals of the Kremlin Cup, rallying to beat Igor Kunitsyn of Russia 6-7 (7/5), 6-1, 6-0 on Thursday.
Earlier, Marion Bartoli of France kept her chances of qualifying for the WTA Championships alive after she beat Ksenia Pervak of Russia 6-1, 6-1 in the second round.
Kunitsyn, who won here in 2008, took the first set in a tiebreaker. But Tipsarevic, ranked 14th, jumped to 4-1 lead in the second set and won the next eight games to seal the match.
"In the first set I wasn't hitting the ball enough. I was mentally there, I was fighting, but I wasn't aggressive," said Tipsarevic, who was runner-up here in 2009.
He said the sixth game of the second set was the key to his victory.
"It was a double break - it's probably a set in the bag - and I started the third set breaking him in the first game," Tipsarevic said.
In Friday's quarter-finals, Tipsarevic will play sixth-seeded Dmitry Tursunov of Russia, who saved four set points in the second set and prevailed in a tiebreaker to beat Julien Benneteau of France 6-3, 7-6 (7/1).
In earlier men's second-round play, Jeremy Chardy of France upset third-seeded Aleksandr Dolgopolov of Ukraine, 6-3, 7-6 (8/6) to set up a quarter-final with Germany's Philipp Kohlschreiber, who ousted seventh-seeded Gilles Muller of Luxembourg, 7-6 (7/4), 6-3.
The third-seeded Bartoli, fresh off her seventh career triumph at the Japan Open, needs to take the title in Moscow to secure the last spot for the season-ending event in Istanbul next week.
"I really do not think of it," Bartoli said. "I'm just trying to fight for every point when I'm on the court and I try to play the best I can. And then we'll see where it takes me."
Agnieszka Radwanska, who leads Bartoli by 330 points, lost to Lucie Safarova on Wednesday to leave Bartoli still hopeful of clinching her place.
After dropping her first serve, the eighth-ranked Bartoli won 11 consecutive games for a set and 5-0 lead.
Pervak then saved five match points on serve before Bartoli closed out the match with an ace.
"For the first 15-20 minutes, there were very tight games," Bartoli said. "And though I was leading, every game was really close. But then I began serving better."
Pervak said she could not find her rhythm and didn't expected Bartoli to play "so strong and be so motivated" in her first match here.
In quarter-finals, Bartoli will play Elena Vesnina, who earlier beat her fellow Russian Ekaterina Ivanova, a qualifier, 6-3, 6-4.
In other women's second round matches, eighth-seeded Dominika Cibulkova of Slovakia beat Klara Zakopalova of the Czech Republic 7-6 (7/5), 6-2.
Sixth-seeded Russian, Svetlana Kuznetsova, advanced to the quarter-finals by beating Tsvetana Pironkova of Bulgaria 7-5, 7-5.
Kuznetsova - a two-time Grand Slam winner - broke decisively in the 11th game of each set.
Results from the fourth day of the Kremlin Cup on Thursday (x denotes seeding):
Dominika Cibulkova (SVK x8) bt Klara Zakopalova (CZE) 7-6 (7/5), 6-2
Marion Bartoli (FRA x3) bt Ksenia Pervak (RUS) 6-1, 6-1
Elena Vesnina (RUS) bt Ekaterina Ivanova (RUS) 6-3, 6-4
Svetlana Kuznetsova (RUS x6) bt Tsvetana Pironkova (BUL) 7-5, 7-5
Janko Tipsarevic (SRB x1) bt Igor Kunitsyn (RUS) 6-7 (5/7), 6-1, 6-0
Dmitry Tursunov (RUS x6) bt Julien Benneteau (FRA) 6-3, 7-6 (7/1)
Philipp Kohlschreiber (GER) bt Gilles Muller (LUX x7) 7-6 (7/4), 6-3
Jeremy Chardy (FRA) bt Aleksandr Dolgopolov (UKR x3) 6-3, 7-6 (8/6)