Spain's Rafael Nadal returns the ball to Greece's Stefanos Tsitsipas during the Mubadala World Tennis Championship Final at Zayed Sports City in Abu Dhabi, on December 21, 2019. Photo: AFP

Towering American Reilly Opelka beat Japan's Yoshihito Nishioka in three sets to win his second career ATP Tour title at the Delray Beach Open in Florida on Sunday.

The fourth-seeded Opelka clinched victory in style, pounding his 27th ace of the match down the centre line for a 7-5, 6-7 (4/7), 6-2 triumph.

"I'm just really proud of the way I fought in the third set," Opelka said. "I got an early break and I broke again. Physically I was feeling pretty good. If he broke me and we had to play more tennis, I was fine."

Opelka won the first set after crushing a forehand at 6-5 to earn his third set point. 

A cross-court backhand passing shot that Nishioka couldn't handle ended the set and sent Opelka, sprinting to his chair, smacking his chest in celebration.

Nishioka forced a tiebreaker in the second, which he won when Opelka sent a groundstroke long.

But the Japanese player double-­faulted in the first game of the third set to give Opelka the break and the 22-year-old American finished off the match with his big ace.

Opelka had surprised Canada's second-seeded Milos Raonic 4-6, 7-6 (6/8), 6-3 in their rain-delayed semifinal earlier on Sunday to set up the meeting with the rested Nishioka.

Nishioka had beaten France's Ugo Humbert 1-6, 6-4, 6-0 on Saturday before rain washed out other matches at the Florida tournament.

Opelka's only other title came a year ago in the New York Open.