Kiki Bertens will retire at the end of the WTA Tour season at the age of 29.

Bertens revealed in a media conference on Wednesday that a combination of the COVID-19 pandemic and an ongoing Achilles injury prompted her to start a new chapter in her life.

A winner of 10 WTA Tour singles and 20 doubles titles, Bertens reached a career-high fourth in the rankings two years ago.

Bertens, now ranked 20th in the world, embarked on her best grand slam run at the 2016 French Open, reaching the semi-finals at Roland Garros.

She was knocked out in the first round of the Paris major Polona Hercog by this time around and made the decision to quit this year after bowing out in the French capital.

Jil Teichmann saved six match points in a stunning defeat of Elina Svitolina before Ash Barty breezed into the second round of the Madrid Open on Thursday.

Teichmann produced an astonishing fightback to beat fourth seed Svitolina 2-6 6-4 7-6 (7-5) at the Caja Magica.

Unseeded Swiss Teichmann came from a set and a break down to claim the scalp of the world number five, who squandered a commanding 5-1 lead in the final set.

Svitolina saw six match points come and go in an incredible deciding set, opportunities she was left to rue when the 40-ranked Teichmann won a tie-break to end a contest that took two hours and 33 minutes to settle.

World number one Barty extended her winning run on clay to 12 matches with a 6-2 6-1 success over Shelby Rogers.

Barty claimed her third title of the year in Stuttgart last weekend and the Australian needed just an hour to send Rogers packing, losing just two points on her first serve and not facing a single break point.

French Open champion Iga Swiatek was also an emphatic winner, easing past another American in the form of Alison Riske 6-1 6-1.

Swiatek, making her debut in this tournament, has won 16 consecutive matches on clay after blowing Riske away.

Defending champion Kiki Bertens beat 15-year-old Victoria Jimenez Kasintseva 6-4 6-0, while Petra Kvitova progressed when opponent Marie Bouzkova retired due to hand injury after the Czech won the first set.

Garbine Muguruza was forced to withdraw ahead of her meeting with Sloane Stephens due to a leg injury. Belinda Bencic, Angelique Kerber and Johanna Konta were among the other winners in the Spanish capital.

Victoria Azarenka booked her spot in the second round of the Qatar Open with a 6-2 6-3 win over Svetlana Kuznetsova on Monday. 

It was the first time the pair had faced off since the final of the 2016 Miami Open and Azarenka, who won back-to-back titles in Doha in 2012 and 2013, struck first, eventually claiming the opening set in 44 minutes. 

She needed six match points to see off Kuznetsova in the second set to tee up a last-16 meeting with either Laura Siegemund or Elena Rybakina. 

There was also a win for former world number one Garbine Muguruza, who defeated Veronika Kudermetova 6-2 7-6 (7-4).

"Veronika was a very tough opponent," Muguruza told a media conference. "[I'm] just happy with this win. We played a year ago, and I remember it was a tough match. I'm happy to have closed it in two sets."

Fifth seed Kiki Bertens, meanwhile, was dumped out by a rampant Jelena Ostapenko in straight sets. 

The 2017 French Open champion hit 26 winners on her way to an emphatic 6-0 6-2 win against her Dutch opponent, who was playing her first match in five months following Achilles surgery. 

Anett Kontaveit overcame number seven seed beaten Australian Open finalist Jennifer Brady 6-1 6-2 to set up a second-round clash with Angelique Kerber, who beat Cagla Buyukakcay 6-4 6-2.

In the day's other match, Maria Sakkari beat Mayar Sherif 6-0 6-3. 

Meanwhile, teenage qualifier Clara Tauson shocked number one seed Ekaterina Alexandrova 6-3 6-4 in the first round of the Lyon Open. 

There were also wins for Arantxa Rus, Nina Stojanovic, Timea Babos, Greet Minnen and Fiona Ferro in France.