MADRID, Spain - No.4 seed Angelique Kerber was forced to withdraw from the Mutua Madrid Open on Tuesday prior to her second round match against Petra Martic with a right ankle injury.

The German defeated Lesia Tsurenko in Sunday's first round, 6-3, 6-2, but proved unable to continue in this week's Premier Mandatory event after twisting her ankle in Tuesday morning practice.

"I think it's not too serious, but I'm not able to give today everything and that's why I decide to be safe for the rest of the clay court season," Kerber told reporters in her ensuing press conference.

"I cannot really walk without pain, so this is why I really said 'Okay, it's better to not risk it,' because I feel it when I'm walking and this is a not a good sign to going on court and giving everything, two or three hours running out there."

Tuesday's match was set to be the fourth career meeting between Kerber and Martic, and first in seven years, but the setback is the latest for the German in an already interrupted clay court season.

She previously suffered from a viral illness which impacted her preparation for the Porsche Tennis Grand Prix, where she reached the quarterfinals. 

"It's not the best clay court preparation. I was looking forward this year to the clay court season and now first with the virus, now with the ankle, it's not really good sign yet," she said.

"But I'm trying. I have still one week to Rome, so I'm going home trying everything I could to be as soon as possible on court again and we have still a few more weeks so hopefully, I can be ready for the next big ones.

"I hope they are big chances to play in Rome. I have still a few days to go. I have to say now, to see the next few days how it's recovered, how I feel the pain or what exactly it is at home. 

"It's still one week and if it would be tomorrow, or two days, I would say the chances are not so good. But if it is one week, the chances are bigger."

Istanbul champion Martic advances to the third round via a walkover, where she will face either Donna Vekic or qualifier Kristyna Pliskova.