Somdev had entered the event as a runner-up and had to defend a lot of points but lost tamely to Serb Janko Tipsarevic in the second round to crash out of India's only ATP event.
Fast rising Yuki Bhambri though gained five positions to reach career best 330.
Indian Davis Cupper Rohan Bopanna also dropped out of top 400 after his first round exit from Chennai Open. His singles ranking slid to 424, a loss of 33 places.
However, doubles specialists Mahesh Bhupathi (7) and Leander Paes (8) had their rankings unchanged.
Meanwhile, in the WTA singles rankings, Sania Mirza rose a rung to 56 despite a second round exit from the Auckland event.
The Indian, however, dropped a rung to 38 in the doubles rankings.