Why Nalbandian is the biggest rival of Federer in his early career?

Rafael Nadal and Novak Djokovic are the biggest rivalries of Roger Federer now. But in the past(2000-2007) David Nalbandian called a biggest rival of Federer. I know a greatest tournament of Nalbandian in Madrid 2007, he defeated top 3 player Nadal, Djokovic and Federer! it's amazing. Nalbandian can give many troubles for Nadal in the baseline