Miami - US fourth seed Reilly Opelka won twice on Sunday to capture the ATP Delray Beach Open title, outlasting Japan's Yoshihito Nishioka 7-5, 6-7 (4/7), 6-2 in the championship match.
It was a second career ATP crown for the 22-year-old American, whose other title came at last year's New York Open, and he won after he played a morning semi-final at the rain-hit Florida venue.
Opelka battled back to eliminate Canadian second seed Milos Raonic 4-6, 7-6 (8/6), 6-3 in the semis to book a date with the world No 63.
"I'm exhausted after those two (matches)," Opelka said.
Nishioka, who won his only prior ATP final in 2018 at Shenzhen, ousted French sixth seed Ugo Humbert 1-6, 6-4, 6-0 on Saturday before the rain.
Opelka beat Nishioka 6-4, 6-4 last week in the second round at the New York Open in their only prior meeting.
Nishioka, 24, is projected to crack the ATP's top 50 for the first time in Monday's rankings.
In the finals tie-breaker, Opelka botched a forehand volley to hand Nishioka a 6-3 edge and the American sent a forehand long two points later to force a third set.
Opelka broke early in the third and again in the seventh game, Nishioka slamming down his racquet in anger after having rescued three break points only to fall behind 5-2.
Opelka held serve a final time to complete the victory after two hours and nine minutes, having spent a combined four hours and 16 minutes on the court for six sets in both matches.
"Yoshi is a great competitor," Opelka said. "He made me run down every ball."
In the semis, Opelka seized a 5-0 lead in the tie-breaker before dropping six points in a row to Raonic, only to fire an ace to save match point and watch the Canadian send two forehands long to force a third set.
Raonic sent a backhand wide to surrender a break in the seventh game of the final set and Opelka blitzed him in the last game to advance.
Results on Sunday from the ATP Delray Beach Open (x denotes seeding):
Reilly Opelka (USA x4) bt Yoshihito Nishioka (JPN) 7-5, 6-7 (4/7), 6-2
Reilly Opelka (USA x4) bt Milos Raonic (CAN x2) 4-6, 7-6 (8/6), 6-3