Ferrer played very well in the two sets, and he has demonstrated the step-up that Nadal has needed to make from now until the finals. As everyone has said, the problem is Ferrer doesn't believe he can beat Rafa over 5 sets. He's probably content with winning 1 at RG.
Novak, however, could be a very different prospect - he won't make this many errors and he won't stop believing.
Meanwhile, Murray has given himself more work to do by losing the 3rd set. He HAS to win the 4th otherwise they'll have to return tomorrow, which would put him at a severe disadvantage against Nadal.