Originally Posted by Netspirit
Not in his prime, 2004-2007, see Wimbledon 2006 and 2007 (and even their clay matches before 2008 ). He only got into his head after Federer self-destructed in the FO 2008 final, which affected his confidence in the Wimbledon 2008 and AO 2009 finals, after which they never met again before Federer was way, way past his slam-winning age.
Even in the matches he lost, no one got as close to winning against Federer in slams with the exception of Safin who in fact beat him in AO2005.
Off the top of my head, I can think of at least 10 matches in which Fed was leading/the score was close before Nad got into Fed's head:
08 Monte Carlo
Nadal is a slow starter but usually picks up his consistency and heaviness of shot over the course of the match, whereas Federer's focus and consistency declines as Nadal's consistency increases. That is how most of their matches in which Federer lost have been played out.