Sharapova needed nearly three hours to beat Cibulkova
Maria Sharapova moved a step closer to the number one ranking, but only after a less than convincing victory over Dominika Cibulkova at the Italian Open.
The 21-year-old Russian won 6-2 3-6 6-4 to advance to the third round.
With current world number one Justine Henin deciding to retire, Sharapova will move to top spot next week.
Her cause was helped by a shock defeat in Rome for world number three Ana Ivanovic, who was beaten 6-4 5-7 6-2 by Bulgarian qualifier Tsvetana Pironkova.
Sharapova has been ranked number one three times before, for a total of 14 weeks, the last time in 2007.
The WTA confirmed on Friday that Henin will be removed from the next world rankings.
Sharapova will commence her 15th career week at number one on Monday, having first reached the top ranking on 22 August, 2005.
"The ranking has never been a big deal for me," she said. "My goal is just to keep winning tennis matches and the ranking will take care of itself."
Ivanovic was never comfortable on the clay and committed 59 unforced errors to Pironkova's 26.
The Serb twice surrendered a break advantage in the second set.
"I really struggled with my intensity today, and that obviously caused a lot of errors," she said.
The Williams sisters both progressed on Wednesday, fifth seed Serena thrashing Alona Bondarenko 6-2 6-0 and Venus, on her return from a month out injured, overcoming Samantha Stosur 6-4 6-1.
Venus had been out for a month with an unspecified medical problem, which she would still not discuss in detail.
Defending champion Jelena Jankovic beat Flavia Pennetta 6-1 6-4, in the Italian's second match of the day, after she had earlier beaten Olga Savchuk in three sets.