Three-time champion Venus stunned by Collins as Ostapenko reaches Miami semis

A three-time champion in Miami, Venus Williams was the overwhelming favourite.

Miami, March 28: Venus Williams and her pursuit of a fourth Miami Open title was stunningly ended by American qualifier Danielle Collins in the quarter-finals.

A three-time champion in Miami, Williams was the overwhelming favourite to move through to the semi-finals but the veteran was upstaged 6-2 6-3 against Collins on Wednesday.

Collins tallied 18 winners – two more than eighth seed Williams – as she sent the seven-time grand slam champion packing from the WTA Premier Mandatory event.

Collins beats V. Williams (6-2 6-3)

It was Collins' first top-10 victory of her career following the 87-minute upset midweek.

"The first time I saw Venus in the locker room, I nearly cried," Collins said. "I mean, I've idolised her my whole life. She's been my favourite player for forever. This is such a special moment, I'm just trying to wrap my head around it."

Next up for Collins is the sixth seed and French Open champion Jelena Ostapenko on Thursday.

Ostapenko outlasted fourth-seeded Ukrainian Elina Svitolina 7-6 (7-3) 7-6 (7-5) to advance to the final four.

With 44 winners and 42 unforced errors, Ostapenko reached her first semi-final of the year.

"Before the match, I knew that I have to be very aggressive," Ostapenko said post-match. "And when I had a chance, I was going for it. Of course, I was missing some because I was trying to play aggressive the whole match, but I think my winners are more than the unforced errors."

Del Potro wins 15th straight match

Meanwhile, there is just no stopping Juan Martin del Potro after the red-hot world number six overcame Milos Raonic in a thrilling quarter-final at the Miami Open.

Acapulco and Indian Wells champion Del Potro extended his winning streak to 15 matches courtesy of Wednesday's 5-7 7-6 (7-1) 7-6 (7-3) victory.

Argentine fifth seed Del Potro lost the opening set against the Canadian and looked out of it as he spoke to a trainer during the set break.

But the resilient Del Potro - seeking back-to-back-to-back trophies - rallied to outlast Raonic after almost three hours and consecutive tie-breaks in Miami midweek.

Del Potro, who celebrated his ATP-best 21st victory of the season, will contest back-to-back Masters 1000 semi-finals.

Standing in the way of Del Potro and a third straight final is in-form American John Isner.

Isner was too good for Australian Open quarter-finalist Chung Hyeon, cruising to a 6-1 6-4 win in only 69 minutes at Crandon Park.

Seeking his maiden Masters crown, Isner - the 14th seed - won 97 per cent of his first serves to advance to his 11th ATP 1000 semi.

"This is actually the best I've moved all year," Isner said. "That's not working harder, or training harder off the court; that's just from me being more confident on the court."

Source: OPTA