Miami Masters PHOTOS: Isner topples Chung; Venus stunned

IMAGES from the matches played at Miami Miasters in Key Biscayne, Florida, on Wednesday

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 US 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.

A fired up Isner yelled "Come on" and pumped his fist when he broke Chung's serve in the first set to race to a 3-1 lead, ending the Korean's streak of 27 consecutive holds of serve.

The 14th-seeded Isner cruised through the remainder of the 25 minute opener, in which he fired seven of his 13 aces.

The hour-long contest was all but over once Chung sent a forehand long in the fifth game of the second set to hand Isner another break and a 3-2 lead.

The 21-year-old was unable to find an answer to Isner's booming serve in a match where he failed to convert his only break point opportunity and was himself broken four times.

"I played extremely well. Every match I've played in this tournament I've gotten better," the 32-year-old Isner said in a courtside interview.

"I keep getting stronger and that's a very, very good sign going forward. I know I'm in the semi-finals and I can't wait to get back on this court."

Isner added that the hot and windy conditions in Miami, where the courts are not particularly fast but cause the ball to bounce high, suit his first-strike approach to the game perfectly.

"Del Potro is the hottest player on tour right now, hands down," Isner added.

The other quarter-finals will be played on Thursday.

Qualifier Collins stuns idol Venus to reach Miami semis

Qualifier Danielle Collins overpowered her childhood idol Venus Williams 6-2, 6-3 in a stunning quarter-final upset at the Miami Open on Wednesday.

Collins, belying her 93rd ranking, pounded winner after winner to beat fellow American Williams at her own game and set up a semi-final against French Open champion Jelena Ostapenko.

Latvian Ostapenko overpowered Ukrainian fourth seed Elina Svitolina in two tiebreaks to win 7-6(3), 7-6(5) in an afternoon match to reach the Miami semis for the first time.

Thursday's other semi will pit American 13th seed Sloane Stephens against unseeded Victoria Azarenka of Belarus.

Collins played with manic intensity against eighth seed Williams, repeatedly going for broke with groundstrokes that painted the lines and ran her opponent ragged around the CrandonPark centre court.

"The first time I saw Venus in the locker room I nearly cried," Collins said in an on-court interview.

"I've idolised her my whole life. She's been my favourite player for forever and this is just a special moment I'm trying to wrap my head around it."

The 24-year-old is finally finding her feet at the highest level, as she showed by keeping the pressure on Williams with victory in sight.

"She's been in a lot of situations where she's been down and come back. I knew I was going to really have to work for it and she wasn't going to give it to me," Collins said of the 37-year-old seven-times grand slam champion.

"I'm just starting to finally put all of the pieces together."

Earlier, sixth seed Ostapenko was far from her best in her quarter-final, spraying the court with 44 unforced errors and having her serve broken six times on a windy day.

Yet the 20-year-old's aggressive approach, stepping into the court to take Svitolina's second serves early and targeting the lines with her powerful backhand, paid off in the match's biggest moments.

After Svitolina saved three consecutive match points in the second set tiebreak, Ostapenko hammered her 41st winner, a crosscourt backhand, on match point to end the nearly two hour contest.

Ostapenko said she followed coach David Taylor's advice to stay on the attack against the defensive-minded Svitolina even when she was having trouble with her accuracy.

"When David came on the court he was telling me to keep playing aggressive, to go for the shots," Ostapenko said on court.

"Even if you are missing you have to play aggressive," she said.

"I'm just trying to fight for every point and be more consistent and I think I'm getting there in my form."

Ostapenko has now won both of her meetings against Svitolina, included a victory over the 23-year-old at Wimbledon last year.