Roger Federer landed his fourth Miami Open crown and 101st career title with a 6-1 6-4 win against a wounded John Isner on Sunday.

The 37-year-old, who suffered disappointment losing to Dominic Thiem in the final at Indian Wells, made up for it at the Hard Rock Stadium venue against the big-serving American to become the first repeat champion in 20 ATP tournaments this year.

Defending champion Isner suffered a heartbreaking end to the final as he struggled to move late in the second set, hampered by pain in his left foot.

Federer, who was playing in his 50th Masters 1000 final, broke Isner three times in a blazing opening set in which he lost just three points on his own serve.

But the American fought back in the second, levelling the set at 3-3 and 4-4 before the pain made it difficult for him to continue and the Swiss maestro soon finished off the job in 63 minutes.

"It was a dream start. Maybe I broke too many times in the first set, I felt like I used too many jokers. I'm so happy right now, it's great," said Federer.

"What a week its been for me. I'm just so happy right now. It's unbelievable. I played here in 1999 for the first time and here I am in 2019. It means a lot to me."

Federer - a 20-time Grand Slam champion - will have to win nine more titles to beat Jimmy Connors' all-time men's record of 109 career titles.