The Bulgarian-American combo pulled out due to Dimitrov's right shoulder injury.
The third seeds will next take on the winners of the match between American top seeds Bob and Mike Bryan and Filipino-American pair of Treat Huey and Scott Lipsky.
The Indian doubles specialist and his Romanian partner defeated Andy Murray and Daniel Nestor 2-6, 6-1, 10-3 in the opening round of the US $1,753,020 hard-court event.
Image: Rohan Bopanna, right with Florin Mergea
Photograph: Twitter
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