Maria Sharapova has overcome Flavia Pennetta 7-5 6-1 to end the US Open champion's hopes of reaching the semi-finals of the WTA Championships in Singapore.

The result means that the former world number one, who has already booked herself a place in the final four, will be joined by Agnieszka Radwanska in the semis after she defeated Simona Halep earlier today.

The Red Group contest started brightly for Pennetta, who needed to win one set to reach the semi-finals, as she broke Sharapova at the first time of asking.

However, the Russian, who has won five Grand Slam titles in her career so far, recovered by breaking twice to take a one-set lead.

From that point on, it was relatively plain sailing for Sharapova as she went an early break up in the second set and later broke again to take a 5-1 lead before wrapping up the match.

The contest was the last of Pennetta's career as she now enters retirement.