updated 09/07/2009 AT 10:00 PM ET
•originally published 09/08/2009 AT 8:00 AM ET
Roger Federer may be the world’s top tennis champion, but when it comes to changing diapers as a first-time dad, he says he is still capable of a double fault.
“Thank God nobody is judging me on it,” Federer told PEOPLE at a press conference Monday following his victory over Spain’s Tommy Robredo at the U.S. Open in New York. “It’s hard! But I’m still trying to be good at it.”
The Swiss pro, 28, and his wife Mirka Vavrinec welcomed twin girls Charlene Riva and Myla Rose on July 23 in Switzerland.