Complex sentence: Bob Bryan and Mike Bryan are the defending champions but lost in the semifinals to Leander Paes and Radek Štepánek, ending their bid to win a calendar grand slam.
Split into simpler sentences: Bob Bryan and Mike Bryan were the defending champions, but lost in the semifinals to Leander Paes and Radek Štěpánek. The loss ended the Bryan brothers' bid to win a calendar grand slam.