Guardiola has always mentioned his desire to one-day coach a national team.
But Fernandinho admits it would be 'impossible' for the Spaniard to coach the five-time world champions.
He told ESPN: "Pep said he wanted to make Brazil a World Cup champion and had an entire strategy to make us a world champion.
"But they didn't want it, because they said that they didn't know if Brazil would accept a foreign coach.
"Once we talked about it, but in a very informal way, more in review. Mainly because of the news that came out in Brazil that claimed he had said that he would like to train Brazil.
"But I believe it is a bit impossible. He said he thinks Brazil and Argentina should always have Brazilian and Argentine coaches. We produce so many players, we have the capacity to produce great coaches.
"Within the more informal conversation I believe it is difficult, but in football there is no certainty about anything."