Kei Nishikori (picture) broke the serve of American John Isner once in the second set and again in the third set and that was enough for the rising Japanese player to claim the Citi Open title in Washington, DC late Sunday.

The second-seeded Nishikori beat Isner 4-6 6-4 6-4 to celebrate his third title of the season and 10th of his career.

“It’s been an amazing year so far,” said the 25-year-old Nishi-kori, who moved up to fourth from fifth in the rankings.

“I’ve had some good Grand Slams, too.”

Nishikori now looks forward to taking the next step at the US Open, where he lost to Marin Cilic in the final last year.

“I defend the final in the US Open, so I will try to keep it going,” he said about his ranking points.

“I’m looking forward to keeping it going at the US Open.”

After Isner broke his serve in the final game of the first set to claim the opening set, Nishikori wasted no time getting back on track.

The Japanese broke Isner in the first game of the second set, and again early in the final set and outsteadied him on the hardcourt to sweep to victory.

“It’s never easy against big servers,” said Nishikori, who lost to Isner in the quarter-finals in Miami earlier this year.

“It was a close game, but I’m happy to avenge.”

Isner, coming off a tournament win last week in Atlanta and playing his 10th match in 12 days, fired 18 aces to Nishikori’s five, but the cool, calm Japanese was sharp with 23 winners and only 13 unforced errors in nearly two hours of tennis.

It was another DC disappointment for 30-year-old Isner, who lost in the Citi Open final for the third time in six years.