Youth has ruled the 2021 clay season so far, with No.1 Ashleigh Barty, No.4 Aryna Sabalenka, and reigning Roland Garros champion Iga Swiatek capturing the biggest titles on European clay. As a result, the talented trio surged up the WTA Insider Clay Court Power Rankings, with Sabalenka making her debut at No.8.

The WTA Insider Clay Court Power Rankings are based on an empirical formula that isolates a player's success rate on clay courts. To measure a player's recent aptitude on the surface, the Insider team applied the following formula, which takes into account a player's results over the last five seasons:

100% of points earned on clay courts in 2021
100% of points earned on clay courts in 2020
75% of points earned on clay courts in 2019
50% of points earned on clay courts in 2018
25% of points earned on clay courts in 2017

The resulting sum accounts for a player's "Clay Court Index." Click here for the previous run of the Power Rankings at the start of the clay season.

With Roland Garros set to begin on Sunday, May 30, here are the Top 10 on the WTA Insider Clay Court Power Rankings:

1. Simona Halep: 4,754.25 pts.
2. Iga Swiatek: 3,511.75 pts.
3. Ashleigh Barty: 3,327.5 pts.
4. Karolina Pliskova: 3,006.50 pts.
5. Kiki Bertens: 2,678.25 pts.
6. Petra Kvitova: 2526.00 pts.
7. Elina Svitolina: 2,393.25 pts.
8. Aryna Sabalenka: 1,959.75 pts.
9. Marketa Vondrousova: 1,899.75 pts.
10. Sloane Stephens: 1,821.25 pts.

Swiatek began the clay season at No.6 on the Power Rankings and rose to No.2 after her run to her first WTA 1000 title at the Internazionali BNL d'Italia, her second title of the season. The 19-year-old Polish phenom now holds two of the three biggest clay titles on tour and sits behind only Simona Halep on the Power Rankings.

Due to injury, Halep has withdrawn from Roland Garros.

Barty made her return to clay a triumphant one. Having been sidelined during the abbreviated clay swing last season and unable to defend her title at Roland Garros, the 25-year-old picked up right where she left off. The Aussie picked up her third title of the year in Stuttgart and followed it up with a run to her first Madrid Open final. Her 13-3 record on clay this season moved her right behind Swiatek at No.3 on the Power Rankings.

Madrid champion Sabalenka is the biggest mover, making her debut at No.8. The 23-year-old Belarusian followed up her run to the Stuttgart final with the first clay title of her career, edging Barty in the final to capture Madrid. 

Aryna Sabalenka and Ashleigh Barty faced off in back-to-back finals in Stuttgart and Madrid.

Photo by WTA/Jimmie48

As a refresher, here's a summary of who has dominated the tour's biggest clay-court titles over that five-year span:

Roland Garros: Iga Swiatek (2020), Ashleigh Barty (2019), Simona Halep (2018), Jelena Ostapenko (2017).
Mutua Madrid Open: Aryna Sabalenka (2021), Kiki Bertens (2019), Petra Kvitova (2018), Simona Halep (2017)
Internazionali BNL d'Italia: Iga Swiatek (2021), Simona Halep (2020), Karolina Pliskova (2019), Elina Svitolina (2017-18).
Porsche Tennis Grand Prix: Ashleigh Barty (2021), Petra Kvitova (2019), Karolina Pliskova (2018), Laura Siegemund (2017).
Volvo Car Open: Veronika Kudermetova (2021), Madison Keys (2019), Kiki Bertens (2018), Daria Kasatkina (2017).

Note: The Mutua Madrid Open, Porsche Tennis Grand Prix and Volvo Car Open were not played in 2020 due to the pandemic.

Watch: Chris Evert and Martina Hingis, in conversation

Here's a more detailed look at the Clay Court Power Rankings Top 10:

No.1 Simona Halep (WTA Rank: No.3)
Career Clay Court Win %: 73.7%
2021 Clay Court Record: 4-3
Notable recent clay court results: 2021 Stuttgart semifinalist, 2020 Rome Champion, 2020 Prague Champion, 2019 Roland Garros quarterfinalist, 2019 Madrid finalist, 2018 Roland Garros Champion, 2018 Rome finalist, 2018 Madrid quarterfinalist, 2017 Roland Garros finalist, 2017 Madrid champion, 2017 Rome finalist.

2020 Roland Garros highlights: Swiatek seals Kenin to claim title

No.2 Iga Swiatek (WTA Rank: No.9)
Career Clay Court Win %: 81.5%
2021 Clay Court Record: 8-1
Notable recent clay court results: 2021 Rome champion, 2020 Roland Garros champion, 2019 Roland Garros Round of 16, 2019 Lugano finalist.

Read: How Swiatek is managing expectations ahead of Roland Garros title defense

No.3 Ashleigh Barty (WTA Rank: No.1)
Career Clay Court Win %: 68.6%
2021 Clay Court Record: 13-3
Notable recent clay court results: 2021 Madrid finalist, 2021 Stuttgart champion, 2019 Roland Garros champion, 2019 Madrid quarterfinalist, 2018 Strasbourg semifinalist.

My Performance: Ashleigh Barty talks about winning the 2021 Porsche Tennis Grand Prix

No.4 Karolina Pliskova (WTA Rank: No.10)
Career Clay Court Win %: 61.3%
2021 Clay Court Record: 7-3
Notable recent clay court results: 2020-2021 Rome finalist, 2019 Rome Champion, 2018 Stuttgart champion, 2018 Madrid semifinalist, 2017 Roland Garros semifinalist, 2017 Rome quarterfinalist.

No.5 Kiki Bertens (WTA Rank: No.17)
Career Clay Court Win %: 70.1%
2021 Clay Court Record: 2-1
Notable recent clay court results: 2020 Roland Garros Round of 16, 2019 Madrid champion, 2019 Rome semifinalist, 2019 Stuttgart semifinalist, 2018 Madrid finalist, 2018 Charleston champion, 2017 Gstaad champion, 2017 Nuremberg champion.

No.6 Petra Kvitova (WTA Rank: No.12)
Career Clay Court Win %: 67.8%
2021 Clay Court Record: 7-4
Notable recent clay court results: 2020 Roland Garros semifinalist, 2019 Stuttgart champion, 2018 Madrid champion, 2018 Prague champion, 2016 Stuttgart semifinalist.

Read: Breaking down the projected Top 32 seeds at Roland Garros

No.7 Elina Svitolina (WTA Rank: No.6)
Career Clay Court Win %: 65.4%
2021 Clay Court Record: 6-3
Notable recent clay court results: 2021 Madrid quarterfinalist, 2021 Stuttgart semifinalist, 2018 and 2017 Rome champion, 2017 Roland Garros quarterfinalist, 2017 Istanbul champion.

No.8 Aryna Sabalenka (WTA Rank: No.4)
Career Clay Court Win %: 63.4%
2021 Clay Court Record: 11-2
Notable recent clay court results: 2021 Madrid champion, 2021 Stuttgart finalist, 2019-2020 Strasbourg semifinalist, 2018 Lugano finalist.

Read: Why Sabalenka's clay-court breakthrough in Madrid is a game-changer

Champion's Reel: How Aryna Sabalenka won Madrid 2021

2021 Madrid

No.9 Marketa Vondrousova (WTA Rank: No.21)
Career Clay Court Win %: 63.0%
2021 Clay Court Record: 1-3
Notable recent clay court results: 2020 Rome semifinalist, 2019 Roland Garros finalist, 2019 Rome quarterfinalist, 2019 Istanbul finalist.

No.10 Sloane Stephens (WTA Rank: No.58)
Career Clay Court Win %: 60.0%
2021 Clay Court Record: 7-4
Notable recent clay court results: 2021 Parma semifinalist, 2019 Roland Garros quarterfinalist, 2019 Madrid semifinalist, 2018 Roland Garros finalist.