It's silly to expect him to immediately start playing at his top level after an absence of nearly 8 months off the tour. He did really well to make the final without dropping a set and he only narrowly lost it (he was a set and a break up and, at one stage, was just 2 points away from winning it). Zeballos was playing really well and was able to exploit Nadal's rusty movement. Kudos to him.
It's going to take more than a handful of matches at a small tournament like Vina del Mar before Nadal starts to play himself into any kind of form after such a long absence. Let's wait and see how he does in the rest of his Latin American swing!
"I have to apologise because I clearly pushed Roger so hard on Thursday!" (Andy Murray on why Federer couldn't play the WTF final).