Errani, also 25, had never advanced past the second round at the French Open before this year, despite a strong clay-court background.

WSJ: French Open 2012: Maria Sharapova's Time to Shine

He came to Paris with little experience on red clay, no experience at the French Open and a Chipotle addiction so strong that he has no interest in fine French cuisine.

WSJ: At the French Open, Jack Sock Is Having a

The reason: All four of the top American hopes possess serves and groundstrokes which are strong enough to be weapons on any surface, and the slow, high bounce on clay brings the ball into their hitting zone with sufficient time for them to set up their shots.

WSJ: Americans Produce Feats on Clay