An ecstatic Roger Federer acknowledged he benefited from a "dream start" as he thumped John Isner in the Miami Open final.

Isner was hampered by a foot problem in the closing stages of the contest and could hardly move in what proved the last game as Federer completed a 6-1 6-4 win.

However, Federer looked unstoppable long before Isner's injury, the 20-time grand slam champion breaking Isner on three occasions in the first set while dropping just three points on his own serve in the match.

Isner is renowned for his serving ability and had won nine out of 10 sets via tie-breaks en route to the final. Yet the American was broken in the opening game on Sunday, setting the tone for a dominant Federer performance.

"That is like a dream start, it just relaxes your nerves," said Federer of his early success on the Isner serve.

"Obviously the last game wasn't real any more, but what a week it's been for me, I'm so happy. It was a great start to the match and I'm so happy right now."

Asked about the unusual circumstances of a final game in which Isner was rendered virtually immobile, Federer said: "I had to keep making him work hard ... I can't let that affect my game. I did well at the end, so I'm just really pleased and, of course, I hope for John it's nothing serious."

Federer has now won four titles in Miami, having made his debut in South Florida 20 years ago.

"It's unbelievable. What a stretch it's been. I'm so happy right now," he added.

"I played here in '99 the very first time and I'm back here in 2019. I've played some unbelievable matches at this event. I'm so happy I came here. It means a lot to me," mentioned Federer after winning his 101st ATP title.