MIAMI, FL, USA - Though World No.1 Naomi Osaka has beaten her share of big players to win back-to-back Grand Slam titles, she is yet to face one rival on the WTA Tour.

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Elder sister Mari is set to make her WTA main draw debut at the Miami Open, and the top seed couldn't be more excited.

"I really enjoy having her around," she said during Wednesday's WTA All-Access Hour at the Hard Rock Stadium. "Most of the time, we’re not playing the same tournaments, so it’s really enjoyable to have her here."

The two played doubles together at the 2016 Toray Pan Pacific Open, but Mari has largely toiled away on the ITF Pro Circuit during her younger sister's meteoric rise - a twist Naomi wouldn't have expected when they began playing.

"Up until I was 15, she was 6-0ing me, like, ridiculous! I don’t know what happened – something finally clicked in my head – but for sure she was beating me. In the win-loss category, she’s still up by a million."

Awarded a main draw wildcard in Miami, Mari was scheduled to play her first round against fellow wildcard Whitney Osuigwe, only to find the day washed out due to rain.

"She’s made a few newbie mistakes. Yesterday, it rained all day, but she came here at 11AM and her match was fourth on. I was like, ‘What are you doing?’ I have to talk to her about that."

The sisters are staying at the same hotel, something the two-time Grand Slam champion - who named Mari as her greatest win back in 2014 - calls a "booster" to her own morale as she attempts to win a first Miami Open title.

"It’s interesting because you can give each other advice, especially if you know who they’re playing. It’s just more of a booster, because most of the time, we’re not playing the same tournaments, so it’s really enjoyable to have her here."

- Naomi Osaka

"Everyone knows Indian Wells and Miami are like two other Grand Slams, so there’s big motivation for me. I won Indian Wells last year and wasn’t able to defend it. I just want to do well here too.

"I grew up watching all these great players winning it, and I think I was at one of the finals one year. Going from a kid in the audience to winning the trophy would mean a lot."

Osaka made a splash last year in Miami, where she backed up her BNP Paribas Open crown with a first win over Serena Williams.

"That match was really big because it was the first time I was able to play her. I came straight off Indian Wells, and I was kind of tired. No matter what, I wanted to play and see what would happen. I was able to win and from there, it felt like a dream in that moment."

An even bigger dream? To play on the WTA Tour full time with her sister.

"I don’t really talk to that many people. She’s the nicer one in this relationship, so it would mean a lot."

Naomi will play her first match against one of two qualifiers - Sachia Vickery or 2009 US Open semifinalist Yanina Wickmayer - while Mari will play Osuigwe on Thursday.