Serena and Cilic advance in China, Nadal loses on return

Serena Williams of the U.S. returns the ball during her women's singles match against Silvia Soler-Espinosa of Spain at the China Open tennis tournament in Beijing September 29, 2014. REUTERS/Petar Kujundzic

BEIJING (Reuters) - U.S. Open champions Marin Cilic and Serena Williams kicked off their China Open campaigns with straight sets victories against battling underdogs on Monday, but Rafa Nadal suffered defeat in a rare doubles outing on his return from injury.

Williams, who won her 18th grand slam singles title in New York earlier this month, started sluggishly and found herself 5-0 and 40-15 down to Spanish qualifier Silvia Soler Espinosa.