Marion Bartoli's shot at ending her lengthy title drought came to an abrupt end at the Western & Southern Financial Group Open when she retired from her first-round match due to abdominal pain.
The top-seeded Frenchwoman, who remains without a WTA singles title since winning at Quebec City in November 2006, was trailing American wild card Jamea Jackson 7-6 (7-5) 2-2 when she could not continue.
Bartoli's withdrawal opens up the top of the draw for fifth-seeded countrywoman Amelie Mauresmo, who needed three sets to outlast compatriot Stephanie Cohen-Aloro 6-7 (5-7) 7-6 (8-6) 6-1, in her first-round match.
Though she has been prone to baffling upsets at times, Bartoli was expected to have few problems with Jackson, who is ranked 415th in the world.
Instead, Jackson broke Bartoli four times and clawed back from a 4-1 deficit in the first-set tiebreak. The American scored another early break to take a 2-0 lead in the second set, but Bartoli broke right back and then held to make it 2-2 before retiring.
Jackson next will play countrywoman Vania King, a 4-6 6-3 7-5 winner over Tathiana Garbin.
Mauresmo, a former number one now ranked 35th, missed roughly four months last season - due to an emergency appendectomy and then a right adductor strain - and has yet to regain the form that lifted her to titles at the Australian Open and Wimbledon in 2006.
She held 4-2 leads in each of the first two sets, only to see Cohen-Aloro battle back to force a tiebreak in each.
The 29-year-old, who hinted at retirement earlier this year, finally took control in the third set, breaking her countrywoman in the opening game and rolling from there to finally prevail in two hours 37 minutes.
Mauresmo, who improved to 21-11 this season, has not won on tour since claiming her 24th career title at Antwerp in February 2007. She will meet Yanina Wickmayer in the next round.
Nadia Petrova, the second seed, had few problems advancing with a 6-3 6-0 win over fellow Russian Galina Voskoboeva. Seeking her first title since February 2007, Petrova will face American Julie Ditty in the second round.
Sixth seed Aleksandra Wozniak also advanced with a 6-3 6-2 rout of Japan's Aiko Nakamura. The 20-year-old became the first Canadian woman in 20 years to win a WTA singles titles with her triumph at Stanford last month.