Who are the 10 best on clay? With the heart of the European clay season just around the corner, WTA Insider goes into the numbers to reveal the 10 best performers on the terre battue.
WTA Insider Courtney Nguyen
April 19, 2018

World No.1 Simona Halep and three-time Roland Garros champion Serena Williams sit atop the WTA Insider Clay Court Power Rankings as the heart of the European clay season is set to get underway next week at the Porsche Tennis Grand Prix in Stuttgart, Germany. Newly-crowned Charleston champion Kiki Bertens, 2016 Roland Garros champion Garbiñe Muguruza, and reigning Roland Garros champion Jelena Ostapenko round out the Power Rankings Top 5. 

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 four seasons:

100% of points earned on clay courts in 2018
100% 
of points earned on clay courts in 2017
75% 
of points earned on clay courts in 2016
50% 
of points earned on clay courts in 2015

The resulting sum accounts for a player's "Clay Court Index."

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

Roland Garros: Jelena Ostapenko (2017), Garbiñe Muguruza (2016), Serena Williams (2015).
Mutua Madrid Open: Simona Halep (2017, 2016), Petra Kvitova (2015).
Internazionali BNL d'Italia: Elina Svitolina (2017), Serena Williams (2016), Maria Sharapova (2015).
Porsche Tennis Grand Prix: Laura Siegemund (2017), Angelique Kerber (2016, 2015)
Volvo Car Open: Kiki Bertens (2018), Daria Kasatkina (2017), Sloane Stephens (2016), Angelique Kerber (2015).

Here are the Top 10 on the WTA Insider Clay Court Power Rankings (as of the week of April 16th). The Power Rankings will be updated throughout the clay court season as the tour makes its way back to Paris for the French Open in May. 

No.1 Simona Halep (WTA Rank: No.1)
Clay Court Index: 4519.00
Career Clay Court Win %: .705
Notable recent clay court results: 2017 Roland Garros finalist, 2017 and 2016 Madrid champion, 2017 Rome finalist, 2016 Roland Garros Round of 16, 2015 Rome semifinalist, 2015 Stuttgart semifinalist.

No.2 Serena Williams (WTA Rank: No.449; Protected ranking: No.1)
Clay Court Index: 2912.5
Career Clay Court Win %: .831 
Notable recent clay court results: 2015 Roland Garros champion, 2016 Roland Garros finalist, 2016 Rome champion. Did not play on clay in 2017. 

No.3 Kiki Bertens (WTA Rank: No.21)
Clay Court Index: 2880.75
Career Clay Court Win %: .681
Notable recent clay court results: 2018 Charleston champion, 2017 Gstaad champion, 2017 and 2016 Nuremberg champion, 2016 Gstaad finalist.

No.4 Garbiñe Muguruza (WTA Rank: No.3)
Clay Court Index: 2777.25
Career Clay Court Win %: .651
Notable recent clay court results: 2016 Roland Garros champion, 2017 and 2016 Rome semifinalist, 2017 Roland Garros Round of 16, 2015 Roland Garros quarterfinalist.

No.5 Jelena Ostapenko (WTA Rank: No.5)
Clay Court Index: 2632.50
Career Clay Court Win %: .692
Notable recent clay court results: Reigning Roland Garros champion, 2017 Charleston finalist, 2017 Prague semifinalist. 

No.6 Elina Svitolina (WTA Rank: No.4)
Clay Court Index: 2322.75
Career Clay Court Win %: .635
Notable recent clay court results: 2017 Rome champion, 2017 Roland Garros quarterfinalist, 2017 Istanbul champion, 2016 Roland Garros Round of 16, 2015 Roland Garros quarterfinalist, 2015 Marrakech champion. 

No.7 Samantha Stosur (WTA Rank: No.58)
Clay Court Index: 2306.25
Career Clay Court Win %: .665
Notable recent clay court results: 2016 Roland Garros semifinalist, 2016 Prague finalist, 2016 Madrid semifinalist, 2015 Strasbourg champion, 2015 Bad Gastein champion. 

No.8 Timea Bacsinszky (WTA Rank: No.46)
Clay Court Index: 2305.00
Career Clay Court Win %: .607
Notable recent clay court results: 2017 and 2015 Roland Garros semifinalist, 2016 Roland Garros quarterfinalist, 2016 Rome quarterfinalist, 2016 Rabat champion, 2016 Gstaad semifinalist.

No.9 Kristina Mladenovic (WTA Rank: No.20)
Clay Court Index: 1838.50
Career Clay Court Win %: .541
Notable recent clay court results: 2017 Roland Garros quarterfinalist, 2017 Madrid finalist, 2017 Stuttgart finalist, 2016 Strasbourg semifinalist, 2015 Strasbourg finalist, 2015 Marrakech semifinalist. 

No.10 Irina-Camelia Begu (WTA Rank: No.38)
Clay Court Index: 1688.00
Career Clay Court Win %: .596
Notable recent clay court results: 2017 Bucharest champion, 2017 Istanbul semifinalist, 2017 Charleston quarterfinalist, 2016 Roland Garros Round of 16, 2016 Madrid quarterfinalist, 2016 Rome semifinalist, 2016 Charleston quarterfinalist, 2016 Florianopolis champion, 2015 Madrid quarterfinalist, 2015 Charleston quarterfinalist.