Sania Mirza gave a tough fight to top seed Patty Schnyder before going down against the Swiss player in the rain-delayed quarterfinal showdown of the USD 175,000 Cincinnati Open tennis tournament.
The ninth seed Indian, who was playing her first quarterfinal of the season, made Schnyder to toil for the 6-7 (7/9), 5-7 victory in the tie which was interrupted twice.
The 19-year-old Sania will now concentrate on her doubles semi-finals, where she is partnering Poland's Marta Domachowska, as the third seeds at the Tier III event.
Schnyder, who is yet to lose a set in the tournament, will be up against fourth seed Katarina Srebotnik of Slovenia in the semi-final en route to winning her 10th title.
Srebotnik overwhelmed sixth-seeded Marion Bartoli of France 6-2, 6-1, to reach her first semi-final of the year.
Schnyder has won both previous meetings between the two, including one at Miami earlier this year.
In the other last eight stage match, Serena Williams advanced to semi-final with a 6-2, 6-2 win over fellow American Amy Frazier.
Williams, who had to wait out the completion of Schnyder-Mirza duel before she got on court in the final match of the evening, made a short work of Frazier despite coming after a long injury lay-off since the Australian Open because of a nagging left knee injury.
The seven-time Grand Slam champion, who has slipped to 139th rank in the world, has been impressive on her return and has not dropped a set while dropping just 12 games in three matches. She will face unseeded Russian Vera Zvonarave, a former top 10 player, in the semi-final.