Former world number one Naomi Osaka moved into the Miami Open semi-finals with a straight-set win over American Danielle Collins.

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.

"This was my first night match so I didn't know what the conditions were like but I was fine and the fans were great," said the 24-year-old.

"I'm glad that, in a way, I don't have a good ranking, because I'm able to play the matches that I need to play. I feel like I'm the type of person that plays better with more matches, so actually having back-to-back matches benefits me a lot."

Semi-final opponent Bencic, 25, has also not lost a set so far in Miami and has beaten Osaka in four of their previous five meetings, most recently at the 2019 US Open.

"I get really emotional when I play people around my age or younger," Osaka added. "I don't know if it's like this thing that I want to be better than them, but I just automatically put a lot of pressure on myself.

"I think my mentality was a very big part in my losses back then. Hopefully, it will be better, because I feel like I have kind of worked through it. So hopefully on Thursday, it will be more about tennis. "