American John Isner won his first ever Masters 1,000 title with a 6-7 (4-7) 6-4 6-4 victory over German Alexander Zverev in the Miami Open final.
In a nervous opening, the first set went with serve before world number five Zverev edged the tie-break.
But 32-year-old Isner twice broke Zverev in the following sets and held his serve throughout the match.
Zverev, 20, saved five break points in the decider but crowd favourite Isner served his 18th ace to seal the title.
The world number 17 will now move back into the top 10 next week after the biggest win of his career.
"I couldn't have scripted this. I came into this tournament, I had won one ATP [World Tour] match all year and was playing very poorly," Isner said.
"I won my first match in three sets and that's how tennis goes - you start to gain a little confidence and next thing you know things start to roll your way."
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Having produced a dominant straight-set victory over the in-form Juan Martin del Potro in the semi-finals, the American's new-found confidence initially deserted him in the final.
After a nervy opening set the final burst into life when Isner squeezed a forehand winner down the line to claim the first break of the match to lead 5-4 in the second.
With the American on set point and serving for the match, Zverev showed tremendous defence to hit two passing shots and take the game back to deuce.
But Isner, backed by a partisan crowd, showed real character to close out the set with a big serve out wide and force a decider.
Zverev struggled on serve in the final set as Isner faced just three break points in the entire match.
The 32-year-old put his three previous major tour final defeats behind him to come back from a set down to win in two hours 29 minutes.
After 32 years at Key Biscayne, the Miami Open will move to a new home next season and with Sloane Stephens having won the women's title on Saturday, America waves goodbye to the historic venue with two home champions.