Flavia Pennetta's career was brought to an end on Thursday as Maria Sharapova eliminated the US Open champion from the WTA Finals in Singapore with a 7-5 6-1 victory.

Agnieszka Radwanska's straight-sets triumph over Simona Halep earlier in the day assured Sharapova of a place in the last four, while ensuring Pennetta - who had already stated her intention to retire at the end of the season - would need to win one set in her final Red Group match to progress alongside the Russian.

Pennetta looked set to claim the set she needed when she moved a break up in the opener, with the aid of several eye-catching returns.

However, Sharapova seized control thereafter and displayed ominous form as she ended the group stage with three wins from as many matches - and provided Radwanska with a semi-final place.

Pennetta initially adopted an aggressive approach against the Sharapova serve, which reaped immediate rewards when a stunning backhand return winner secured the opening game.

Sharapova was forced to save two further break points at 3-2 down - the second with an ace down the T - as Pennetta continued to go for her shots.

However, the Italian was the architect of her own downfall as she served two double faults in the eighth game, enabling Sharapova to get back on level terms with a backhand volley.

And the five-time grand slam champion then claimed a crucial second break, overpowering Pennetta as the latter served to stay in the set.

All the momentum was with Sharapova, whose level continued to rise as she raced into a 3-0 lead at the start of set two.

Pennetta showed great resolve to save two break points en route to a much-needed hold in game four, prior to an unexpected delay as repairs were made to the net.

Yet the end was nigh when Pennetta double-faulted at 30-40 in her next service game and Sharapova made no mistake in serving out the match.