Juan Martin del Potro says the courts at the Sydney International are playing extremely quick with a low bounce, and he's concerned the Australian Open courts will also play fast.

Last week, Marin Cilic called the Brisbane courts the fastest he's ever seen. Roger Federer and Lleyton Hewitt also called Brisbane quick. Both Federer and Hewitt have advocated for faster hard courts on tour.

“I think the bounce are really low,” said the 6'6" del Potro, who likes time to set up for his shots. “Looks like a grass court, because very low bounce and very faster bounce, too. It's not easy to play on the baseline and feel good on the lines, but I'm trying to do the best I can. If I keep winning, it's a good signal for me.”

Del Potro, who will play Dmitry Tursunov in the Sydney semifinals, has had success on grass before, winning the bronze medal at the London Olympics and reaching the 2013 Wimbledon semifinals. But he says he is not prepared for the faster Australian court speed.

“I'm not training for this kind of conditions. I been practicing in hard court, regular hard court, and I was expecting different conditions for this tournament," del Potro said. "Hopefully for Melbourne the courts and balls are slower to play long rallies, to feel the ball like I want. If not, I will have a couple days before start to change my mind and try to play the best tennis I can.”

Petra Kvitova, who lost to former Wimbledon semifinalist Tsvetana Pironkova in the Sydney semifinals, also believes the court speed has increased.

“The courts are faster than last year or two years ago,” she said. "Actually I was happy that they were faster than before, but [Pironkova] likes grass as me… But of course that I prefer this faster surface."