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.

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 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."