The Indo-Romanian pair were always playing catch up in their 3-6, 4-6 loss against their much-experienced American opponents in the hard-court event at the William H.G. FitzGerald Tennis Center.
Bopanna-Mergea entered the final-four stage after receiving a walkover from Bulgarian-American combine of Grigor Dimitrov and Mardy Fish.
The Bryan brothers will now face the second-seeded Brazil-Croat pair of Marcelo Melo and Ivan Dodig at the 1.5 million USD event.