Del Potro, who arrived in Miami having won the Indian Wells Masters earlier this month, recovered from a set down to beat the Canadian 5-7, 7-6, 7-6.

The 2009 US Open winner maintained his superb run of form as he recorded his 15th straight triumph on the tour.

Del Potro's opponent in the last four will be big-serving American John Isner, who ruthlessly dispatched South Korea's Hyeon Chung in the quarter-finals.

Isner, who knocked out second seed Marin Cilic of Croatia yesterday, overcame the Australian Open semi-finalist 6-1, 6-4 in a match which lasted just over an hour.

"I played extremely well," the American said.

"Every match I've played in this tournament, I've gotten better. 

"I've gotten stronger, and that's a very, very good sign."

Fourth seed Alexander Zverev of Germany takes on Croatian Borna Ćorić and Pablo Carreño Busta of Spain plays South African sixth seed Kevin Anderson in the last two men's quarter-finals.

In the women's event, American Danielle Collins stunned eighth seed and compatriot Venus Williams with a comfortable straight-sets win.

Collins dropped just five games on her way to a 6-2, 6-3 success to set up a semi-final clash with Latvian Jeļena Ostapenko, the sixth seed.

Ostapenko progressed with a 7-6, 7-6 victory in her match with Ukrainian Elena Svitolina, the fourth seed.

Victoria Azarenka of Belarus and US Open champion Sloane Stephens will compete in the other women's semi-final.

The tournament in Miami continues tomorrow.