Kei Nishikori, who defended the U.S. National Indoor Tennis Championships for his fourth career ATP title last week, downed Gastao Elias of Portugal in three sets in the first round of the Delray Beach Open on Tuesday.

World No. 15 Nishikori, who won his first title on the ATP tour at this tournament in 2008 when it was called the Delray Beach International Tennis Championships, defeated the 169th-ranked Elias 6-1, 5-7, 6-2 to reach the second round.

The third seed here, Nishikori breezed past his opponent in the first set but lost his rhythm with a series of errors as he was broken in the 12th game and dropped the second.

Nishikori broke Elias in the first game of the third set to regain the momentum as he took a 5-0 lead.

"The ball feels different playing indoors (like last week) and outdoors, and even though I'm not used to that, I played well in the first and third sets," Nishikori said. "For starters, I'd say I played a fine game," he said.