SNZ hopes his expertise will rub off on the country's best swimmers who, with the notable exception of Lauren Boyle and to a degree Glenn Snyders, were a disappointment in London.
There is a similarity in swimming's middle-tier place in the sporting pecking order in Spain and New Zealand. But Villanueva sees one sharp distinction between the countries.
"I come from a country with 40 million people, but with a not very good sports culture.
"In New Zealand, you have a small country with a very good sports culture. Sport is more ingrained on people here than in Spain.
"The organisation of sports is completely different."
Villanueva has been finding his feet since starting the job about four months ago. SNZ will have discovered they haven't hired a fist-slapping, voluble coach. His style is quieter but his message is clear. Take his expectations of the swimmers in Barcelona.
"Overall a good outcome would be to have every swimmer perform faster than they did in the [national] trials. This is the first thing; then to have them swim faster than the last race.
"So it is not good if you swim very fast in the heats but then perform lower in the semifinal, or do a good semi and not be able to do it in the final."
One swimmer at the Olympics who flopped badly talked of finding it hard to produce strong swims twice a day.
"This is something that should be addressed in training," Villanueva said. "You have to be prepared to face challenges in the morning and afternoon, today, tomorrow and the next day. This is what I want to instil in them and in the coaches. You have to put them in difficult situations every day.
"Most swimmers who go to the Olympics need to swim personal bests in the morning, then in the afternoon."
Some swimmers have said they won't improve on the bigger stages unless there are more opportunities to compete against the best.
But Villanueva believes that is only part of the equation.
"Mentally you have to cope with difficult situations. Everything is up here," he said, pointing to his head. "Swimmers have to be sure they are training harder than any others in the world, doing things they didn't think they were capable of. This can be taught in training.
"If you expect this situation to be solved only by facing international competition and don't address mental toughness in training, the chances are you won't [make it]."
Bluntly, he said if swimmers had not tested themselves, pushed themselves to the limit repeatedly in training, "it's impossible that you go to the Olympics and succeed".
Villanueva's role is "trying to improve the results of New Zealand swimmers on the world stage". Barcelona will give him, and newly appointed head coach Briton David Lyles their first real benchmark to work with.
