INDIAN WELLS, CA, USA - Having not lost a match since January, Belinda Bencic might've scored her biggest win yet on Tuesday in Indian Wells.

The No.23 seed ousted defending champion and World No.1 Naomi Osaka in 65 minutes to advance to the quarterfinals of the BNP Paribas Open, 6-3, 6-1.

As it happened: As it happened: Bencic overwhelms Osaka to extend win streak to 11

"She's the No. 1 player in the world. She won everything in the past couple of months," Bencic told reporters after the match. "I played I think a great match. I'm really happy with myself. 

"I think I served really good. The first set was great for me, and then I just tried to keep it like that. It was a little bit more windy in the second set, but I think tactic-wise, I played very solid."

The Swiss scored her second career win against a reigning World No.1, having also defeated Serena Williams en route to winning the Rogers Cup in Toronto four years ago.

Tuesday's match against Osaka was also the first-ever match for Bencic against a No.1 not named Williams, as she lost her first career match against the American when she occupied the top spot in Madrid in 2014.

Bencic improved to 5-0 in matches against the Top 10 this season, having beaten four Top 10 players to win the crown at the Dubai Duty Free Tennis Championships, and extended her season-long winning streak to 11 matches. 

The Swiss No.1 was quick out of the gates, building a 5-1 lead in the first set and losing just two points on serve over that time.

Though Osaka crept closer, winning two straight games and two points from a third, a perfectly-placed backhand return winner gave Bencic the set.

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"I definitely think we both like to take the ball early, so definitely my plan today was -- I mean, not just today, but I'm trying to take the ball early, trying to dictate the point myself. I think definitely she has a little bit more spin on her ball than me," Bencic added.

"I really wasn't focusing so much on her. I was focusing on my game. I'm very confident with my game right now. I'm hitting the ball well. So just things worked out for me."

The second set proved more of the same, with Osaka unable to counteract 28 unforced errors for the match with just 10 winners. 

To her credit, Bencic won over 80 percent of the points played behind her first serves, despite only landing 61 percent of them, and proved incredibly effective on return in the match as well.

Breaking serve five times, Bencic won over 60 percent of the points played when Osaka was forced to hit a second serve - which, for the World No.1, came on exactly 50 percent of the points in her service games.

Even with the defeat, Osaka will maintain her hold on the No.1 ranking through the Miami Open.

Bencic will next face Karolina Pliskova for a spot in the semifinals, after the Czech outlasted Anett Kontaveit in three sets in her round of 16 match.

"I know her well. We are good friends also with her sister. We practiced a lot together. Obviously she has great serve and she's playing very flat and fast," Bencic assessed.

"I think again, I will just focus on my game, of course, a little bit tactical things, but I will think of that tomorrow. I don't like to think so much ahead of the match. Sometimes I feel like the less I think on the court, the better it is."