Novak Djokovic remains on course for a 'Golden Slam' after ruthlessly ending the dreams of home hope Kei Nishikori to cruise into the Olympic semi-finals.
The world number one, bidding to become the first man to win all four Grand Slam titles and an Olympic gold in the same year, breezed through 6-2 6-0.
He will face Germany's Alexander Zverev or France's Jeremy Chardy in the semis.
Earlier, Switzerland's Belinda Bencic beat Elena Rybakina 7-6 (7-2) 4-6 6-3 to reach the women's singles final.
The Swiss will meet the winner of Thursday's remaining semi-final between Ukraine's Elina Svitolina and Marketa Vondrousova of the Czech Republic.