The Russian has recovered from the ankle injury she suffered in Tokyo last month and needs to reach the final in Istanbul to have a chance of overtaking the Dane.
The three-time grand slam champion last finished the year at the top of the world rankings as a 17-year-old back in 2004, but she now has the chance to usurp Caroline Wozniacki at the top of the pile.
The pair will not meet until at least the semi-finals in Istanbul, with world No. 2 Sharapova drawn in the White Group, while Wozniacki heads the Red Group.
Kim Clijsters completed a dream season by capturing the title last year in Doha, Qatar, where the event was held from 2008 to 2010. This year the tournament will be played at the Sinam Erdem Arena in Istanbul. Martina Navratilova has the tournament record with eight singles titles.