NEW YORK -- Growing up, Erika and Mirra Andreeva played some savage practice sets. Erika, three years older, always won.

“Yes,” Erika said Monday at the US Open, “but, honestly, Mirra was so small. The time that we played was very long ago. Also, when you are that young, the age difference matters more.”

“Now, I don’t know how it would go.”

That’s because Mirra, 17, is suddenly one of the world’s best players.

So when did she start beating her older sister?

“I actually haven’t,” Mirra said, laughing. “We practiced a lot when we were younger and of course she would always beat me like 6-1 or 6-2. Maybe only 6-3 if I played good or she had a bad day. But, yeah, we don’t really practice together often. We practice but we don’t play points.”

A year ago, Mirra broke through in Madrid, reaching the Round of 16, where she lost to Aryna Sabalenka. This year, she got to the quarters in Madrid before falling to Sabalenka again. Mirra’s ranked No.23 and reached the semifinals this year at Roland Garros.

She says a lot of her success can be attributed to the early example provided by 20-year-old Erika, who Monday at the US Open won her first-round match 6-3, 7-6 (7) win over Yuan Yue. 

Mirra Andreeva

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“I didn’t watch because I was very nervous,” Mirra said. “So I stayed in the locker room. I was just watching the score. Of course, I was very excited and after the match we met and shared some emotions.”

On Wednesday, Erika, the Hologic WTA Tour’s No.75-ranked player, will go for her first-career second-round victory in a Grand Slam. Her daunting opponent: Olympic gold medalist Zheng Qinwen.

On Tuesday, Mirra was a 6-2, 7-6 (4) winner over Camila Orsorio. This is the first time that sisters have reached the second round at the US Open in three years, when Karolina and Kristyna Pliskova managed that feat.

They say it takes a village to raise a child, but clearly having a sister can be an asset for a future tennis player.

Erika Andreeva

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That scenario is also in play with the Czech Republic’s Linda and Brenda Fruhvirtova. Linda, 19, made the first big impression, advancing to the Round of 16 at last year’s Australian Open and ultimately reaching a career-high ranking of No.49. 

Linda lost in the first round of qualifying at this US Open. Brenda, 17 and ranked No. 106, got into the main draw but lost after retiring with an injury three games in. In the first round at Wimbledon, Brenda defeated Mirra Andreeva -- the only younger player ranked ahead of her, by a scant four weeks.

There’s another player who was in the draw that owes a debt to her older sister.

Karolina Pliskova, a former World No.1, has a twin sister Kristyna -- who was born two minutes earlier. They both first picked up the racquet at the age of four. Kristyna had a career-high of No.35, won a singles title (2016 in Tashkent) and won more than $3 million.

And career bragging rights. The Pliskovas played nine times in their careers, and Krystina -- now retired -- holds an irreversible 5-4 head-to-head advantage over her former top-ranked twin. 

Pliskova sisters

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Serena Williams, famously learned in the shadow of older sister Venus -- and was the first to win a Grand Slam, at the US Open as a teenager. Venus has seven major titles, but Serena ultimately surpassed her with an Open Era record of 23.

Four-time Grand Slam winner Naomi Osaka credits older sister Mari with her rise to the top of tennis.

“If she wasn’t there I wouldn’t be where I am right now,” Osaka told CNN Sport in 2019. “Growing up there was always the two of us, and I would always get inspired by her and she would constantly beat me, so that was kind of a very big motivation for me.”

In her brief career, Mari reached four ITF finals.

A few weeks ago in Toronto, Leylah Fernandez lost a second-round singles match to qualifier Ashlyn Krueger.

“Yesterday’s singles loss felt horrible,” Fernandez wrote on social media. “I am very disappointed with how I played and left the court angry at myself. I didn’t know how I was going to put myself together and compete again in doubles.

“The truth is, my sister [20-year-old Bianca] stepped it up for us. Our dad and coach gave her the green light to take the lead, and she did. I am so proud of her. That win was all her.”

That stirring win came in a 12-10 super-tiebreak over Kristina Mladenovic and Zhang Shuai -- and launched the Fernandez sisters into the quarterfinals.

Mirra Andreeva describes her older sister as a role model, someone from whom she learned what it meant to be a professional.

“I used to watch her practices,” Mirra said. “I was going at 9 [o’clock]. And she was going at 7 a.m. I was like, `Man, what are you doing? Why don’t you want to sleep?’ She was always trying to practice the most and the hardest, and that way I looked up to her.”

For Erika, the success of her younger sister is a double-edged sword.

“Honestly, it motivates me a lot but also sometimes it puts a lot of pressure on me,” she said. “I have always been the older one, and I wasn’t like a role model for her, but I tried to show her my best so that she could copy me. 

“And now I feel it’s a bit the opposite, but I think it still works well.”

How has Mirra’s success inspired Erika?

“I actually don’t know,” Mirra said. “Because I don’t really like to talk about it with her. I feel like maybe she can feel a little bit of pressure. Maybe she feels like she had to do it first because she is older.

“But I think that there is a right time for everyone. And maybe for me it was a bit earlier. And maybe for her the time is coming now.”