A week ago, Petra Kvitova announced her mononucleosis diagnosis to the world. After a 6-2, 6-3 loss to Victoria Azarenka last week in Montreal, the World No. 4 says she’s trying to spend more time on the court in order to avoid coming out flat like she did in that one-sided loss to Azarenka. But it’s a tricky equation now for the two-time major champion. Just how much endurance work she is capable of doing, she is not sure.

More: Kvitova Talks about Mononucleosis Diagnosis

“When we found out about the mono we were like cutting almost everything, I was just practicing for an hour in the morning, have 30 minutes of fitness in the afternoon—be more relaxed,” Kvitova told reporters at a media round table on Monday at the Western and Southern Open in Cincinnati. “The same kind of situation was [what we did] in Toronto.”

Kvitova says the 90 minute of practice wasn’t enough to get her in the groove, so this week in Cincinnati she’s pushing it a bit more.

“When I saw how I’m playing against Vika, that I didn’t really have too many hours on the court [I realized I needed more practice],” she said. “This time I practiced an hour in the morning and an hour in the afternoon.”

So far, so good, but Kvitova comes across as somebody who isn’t quite sure what her body will allow her to accomplish during the final quarter of the 2015 tennis season. “I hope I will be fine,” she said. “I never know actually. It’s really up and down, I never know.”

She added: “If the doctors will tell me to stop for a couple of months, I will. But they allowed me to play and not really do too much. I will see how it is going. It’s really tough to say anything.”