Juan Martin del Potro closes in on Miami Open after outlasting Milos Raonic

Del Potro will face American John Isner in the semi-finals

Del Potro is looking to win the Miami Open on the back of his Indian Wells title (Getty)

Juan Martin del Potro remained on course for a rare Sunshine Double when he outlasted Milos Raonic 5-7 7-6(1) 7-6(3) in a marathon quarter-final at the Miami Open on Wednesday.

Del Potro, who claimed the Indian Wells title earlier this month, fed off the energy of a raucous crowd that was firmly behind the Argentine, wearing down the 20th-seeded Canadian in a match lasting almost three hours.

The clock had just struck midnight on an unusually cool evening when fifth seed Del Potro finally dispatched Raonic.

The Canadian was defeated despite not facing a single break point in the first two sets, before the contest took a bizarre twist at the start of the decider when both players were broken twice in a row.

Order was soon restored as both men held for the next eight games, sending the contest to a deciding tiebreak, in which Raonic never recovered after double-faulting to fall 2-0 down.

The result continued Del Potro's hot streak, after he won in California 10 days ago, beating Roger Federer in a compelling three-set final to claim a maiden Masters 1000 title.

The 2009 U.S. Open champion is back to playing some of his best tennis in years after battling serious left wrist injuries that required three surgeries and threatened to curtail his career.

He advances to face another big server, American John Isner, who overwhelmed South Korean Chung Hyeon 6-1 6-4 in an afternoon match.

Venus Williams has been knocked out of the Miami Open at the quarter-finals by the qualifier Danielle Collins 6-2 6-3.

Seven-time Grand Slam winner Williams went a break down in the first set as American Collins raced to a 3-0 lead, and saved two set points at 5-2 but lost the third after 39 minutes.

The second set went a similar way with Collins, ranked 93rd, breaking at the first opportunity for a 2-0 lead, but Williams broke back for 2-1.

But Collins, 24, broke to take a 4-2 lead and booked her place in the semi-final on the second of her match points.