Sania Mirza dropped to No 70 in the latest WTA rankings, released on Monday.
The Indian teenager, who began the US Open ranked 54, fell 16 places following a second round exit at Flushing Meadows.
Sania lost 5-7, 6-1, 6-2 to Italy's Francesca Schiavone, unable to reproduce her showing at the Open last year when she made it to the fourth round.
Leander Paes, who teamed with Martin Damm for his seventh Grand Slam triumph on Saturday, moved into the top 10 of the doubles rankings.
The 33-year-old Paes is now ranked No 9, while his Czech partner Damm is 10th.
Mahesh Bhupathi, having lost in the opening rounds of the men's and mixed doubles, slipped two places to 29.
Though Sania has shown improvement in her game, she is unable to replicate last year's success, as her opponents have worked her out and are exploting the lack of on-court speed and a weak serve.
The Hyderabad ace has just one quarter-final appearance in WTA events this year.
US-based Shikha Uberoi dropped three places and is ranked 194.
France's Amelie Mauresmo, with two majors in her kitty this year, continues to lead the pack with 3610 points.
Newly-crowned US Open champion Maria Sharapova jumped a place to take number three position, behind Mauresmo and Belgium's Justine-Henin Hardenne in that order.
