Aug 1, 2017; Washington, DC, USA; Jack Sock of the United States hits a forehand against Marius Copil of Romania (not pictured) on day two of the Citi Open at Fitzgerald Tennis Center. Sock won 7-6(2), 7-6(6). Mandatory Credit: Geoff Burke-USA TODAY Sports

Eighth-seeded Jack Sock defeated Marius Copil, 7-6 (7-2), 7-6 (8-6), in a rain-delayed opening match for the American of the Citi Open at Rock Creek Park Tennis Center on Tuesday.

The two were deadlocked at 5 in the first set when the rains arrived. Play was suspended briefly, the players returned to the court, then they were sent off again as another storm front rolled in. Play resumed over three hours later.

Sock said the rain delay didn’t bother him, and his blistering serve was strong evidence. He credited the Romanian Copil for his play.

“He’s a very tricky player and tough opponent for sure on a court like this,” Sock said. “It is a little bit quicker than last week and he serves cannons. He has a great first serve and great second serve. He really gets up on this court so not an easy break at all and definitely happy to get out of there in straights.”

Sock, the highest-seeded American in the Citi Open field, will play either Australia’s Marc Polmans or American Jared Donaldson in the second round.

Sock, 24, is ranked No. 19 in the ATP rankings. Fellow American John Isner, who withdrew from the Citi Open on Monday with a knee injury, is the top-ranked American at No. 18. Isner won his fourth ATP Atlanta title on Sunday.

Sock, a two-time quarterfinalist here, has won three singles titles in his career after turning pro in 2011.

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