Former world number one Naomi Osaka moved into the Miami Open semi-finals with a straight-set win over American Danielle Collins.
The Japanese four-time Grand Slam champion, who has yet to drop a set in the tournament, served 13 aces in a 6-2 6-1 win that lasted exactly an hour.
Australian Open finalist Collins appeared to be struggling with a neck injury throughout the match.
Osaka will play Belinda Bencic of Switzerland in the semi-finals.
Olympic champion Bencic beat Australia's Daria Saville 6-1 6-2 to reach the last four.
Osaka, who was reduced to tears by a heckler during her second-round exit at Indian Wells this month, is playing just her fourth event since taking a break from tennis in September, and has dropped to 77th in the world rankings.