It is not only Nadal who fails to reach Federer. Federer failed to reach Nadal at Wimbledon 2010 and 2011, as well as U.S Open 2010 and 2011, all where he was fully expected to play him. Although good thing for him he did, as not only would he have a losing record vs Nadal on grass now (and a now scary 2-12 slam H2H) but Nadal would gain 2 additional slams and be right at Federer's doorstep in slam wins already. Federer wisely allowed the tougher opponent (Djokovic) to make it to Nadal instead, and at times got assistance for the wise choice. Other times Nadal failed such as Wimbledon 2013, Federer did too, so it wouldn't matter. Wimbledon 2012 and 2014 are the only times Nadal really failed to reach his appointed confrontation with Federer, while Federer did more often if anything.
Most of the times Nadal is somehow faulted for not reaching Federer is when he was 18-21, yet Federer at that age couldn't even make it past the round of 16 of a hard court slam ever. :lol: Atleast Nadal at that age was winning on his best surface.