Sania Mirza's steep slide in tennis rankings continued as she lost 21 places to be placed 91st in the latest Women's Tennis Association (WTA) rankings released on Monday.

Sania, who is suffering from a wrist injury, was at the 70th position last week. The Indian has seen a massive dip in her rankings since undergoing a wrist surgery in April.

She made an early comeback on the circuit with the DFS Classic tournament in Birmingham in June which though was followed by a series of early exits.

Sania retired in tears from the first round of her maiden Olympics after the pain on her wrist recurred. Later, she pulled out of the US Open.

Meanwhile, US open champion Serena Williams reclaimed the top spot in WTA rankings dispatching Serb Ana Ivanovic who has fallen to third. US open finalist Jelena Jankovic of Serbia remains at second position.