Last year's beaten finalist, Nishikori will face Argentine Federico Delbonis who beat Germany's Jan-Lennard Struff.

Verdasco has yet to post a win against a top ten opponent this year but showed plenty of spirit in a two hours 44 minute contest on centre court at Crandon Park fighting back to win a second set tie-break.

But Nishikori stepped up in the third, running away with the set to ensure his progress.

France's Nicolas Mahut beat Argentine Guido Pella 6-4 6-3 and will face the winner of Sunday's clash between Rafa Nadal and Germany's Philipp Kohlschreiber in the last 16.

Injury-plagued world number five Milos Raonic pulled out of the tournament shortly before his match against American Jared Donaldson, citing a recurrence of a hamstring injury.

Raonic originally suffered the injury in the semi-final at Delray Beach and was forced to forfeit the final against American Jack Sock. He then missed this month's Masters event at Indian Wells.