The 2018 Volvo Car Open champion will have to work overtime on Sunday.

Rain storms interrupted the tournament's semifinals on Saturday at the Family Circle Tennis Center on Daniel Island, forcing VCO officials to double up on the semifinals and championship match on Sunday's schedule.

No. 7 seed Madison Keys and No 12 Kiki Bertens will play their semifinal match at 10:30 a.m. Sunday on stadium court. No. 5 Julia Goerges and No. 8 Anastasija Sevastova, tied at 4-4 in the first set when the rains came Saturday, will finish their match following Keys-Bertens.

The doubles final will be the third match on stadium court, followed by the singles final.

"It's going to be a tough match," Bertens said of her semifinal with Keys. "(She) is hitting the ball so hard. I have to defend a lot,and play aggressive where I can, and then we'll see how that goes."

Bertens, a 26-year-old from the Netherlands, injured her hip during her 6-3, 7-5 win over No. 14 Alize Cornet on Friday.

"The treatment was good," she said after that match. "It got locked a little bit, so I needed the trainer to just release it a little bit. Of course, I was still a little bit struggling after that. But I'm just going to recover now and go back in again, and hopefully it will be fine."

Keys and Bertens have met only once before, with Bertens winning in straight sets on clay at the French Open in 2016.

Sevastova, a 27-year-old from Latvia, jumped to a 3-1 lead in her semifinal Saturday against Goerges, who fought back for 4-4 when rain stopped the match. Sevastova defeated Goerges, a 29-year-old from Germany, last month on hardcourts at Indian Wells.

All four semifinalists have won titles on the WTA Tour. Goerges and Bertens have four titles each, Keys has won three times and Sevastova has two wins.

At 10:30 a.m. on the Althea Gibson Club Court, the doubles semifinal between the teams of Kateryna Bonarenko/Aleksandra Krunic and Alla Kurdryavtseva/Katarina Srebotnik will be played. Andreja Klepac and Maria Jose Martinez teamed to defeat Mihaela Buzarnescu and Heather Watson, 6-4, 6-0, in Saturday's semifinal.

The PowerShares Series, featuring Michael Chang, Andy Roddick, Mark Philippoussis and Tommy Haas, has been postponed from Saturday night to 8 a.m. Sunday.

The Volvo Car Open is offering full refunds to all ticket buyers for the PowerShares Series, which will happen automatically through point of purchase. Fans can attend the Powershares Series matches for free on Sunday.

Reach Jeff Hartsell at 843-937-5596. Follow on Twitter @Jeff_fromthePC