Juan Martin del Potro is three-for-three at Washington. D.C.’s Citi Open…

The 24-year-old Argentine tennis star, the tournament’s top seed, defeated John Isner 3-6, 6-1, 6-2  in the Citi Open final on Sunday to claim his third championship and 14th consecutive match in Washington.

“His forehand is widely regarded as maybe the best in the world,” said Isner. “I couldn’t do anything about it. I actually wasn’t really surprised. I’ve seen him do that a lot of times. That’s what he does. He’s got a lot of talent, and a lot of talent on that forehand side.”

Back in 2009, del Potro followed up a title in the nation’s capital with a trophy at the U.S. Open, which starts in three weeks.

“Fantastic memories,” the seventh-ranked del Potro told the crowd.

When the Argentine arrived in Washington this time, he came with some questions about his body and his game. He hadn’t played a hard-court match since the spring. He hadn’t competed at all in nearly a month — a five-set loss on July 5 to No. 1 Novak Djokovic in the longest semifinal in Wimbledon history, more than 4½ hours. And he hadn’t fully tested the left knee he hyperextended in a tumble during a match at the All England Club.

“I’m surprised to win this tournament,” del Potro said.

del Potro added to his Washington titles from 2008 and 2009. He skipped the tournament for various reasons from 2010-12.

Next for del Potro are hard-court tournaments in Montreal and Cincinnati. Those lead up to the U.S. Open, where Isner said del Potro will be “certainly one of the top favorites.”