Andy Roddick says the "lethargy" he complained about at Washington two weeks ago has been diagnosed as a mild case of mononucleosis.

"I've been dealing with a mild, mild case of mono for the last couple of months that I wasn't really sure about," he told reporters in Cincinnati. "They think I'm most of the way through it, if not all the way through it.

"More than anything, it's kind of a mental relief as opposed to wondering why, if I was out of out of shape."

Roddick did not identify when the virus first hit, but pulled out of May's claycourt event in Madrid with a stomach bug -- reminscent of Roger Federer's stomach problem in January 2008 that was evenually diagnosed as mononucleosis.