De Gea also made an uncharacteristic error during a pre-tournament friendly clash with Switzerland, with a usually reliable performer seeing his high standards dip.
Nacho, though, has no concerns when it comes to the Premier League Golden Glove winner, with the 27-year-old being backed to remain an important figure for Spain.
The Madrid defender told reporters on De Gea’s response to his outing against Portugal, and that of the squad as a whole: “He seems fine to me.
“He knows what happened but, as players, we are always exposed to these things. When mishaps happen, we unite and we're all with him 100 per cent.
“He is a world-class goalkeeper and we are lucky to have a player of his calibre. He has no doubts about his own ability and he will bring a lot to the team in the future.”
While De Gea gifted one goal to Ronaldo, Nacho was responsible for his club colleague opening the scoring from the penalty spot after tripping him inside the box.
He added on that incident: “These kinds of moves are very difficult for a defender, there was contact, I touched Cristiano but I tried to withdraw my foot.
“It happens so fast that it's more difficult than it might seem.”
Nacho made amends with a stunning second-half strike – his first for Spain – and believes that the goals will continue to flow for Fernando Hierro’s side in upcoming Group B clashes with Iran and Morocco.
The 28-year-old full-back added: “We're not having any problems scoring, we have a lot of faith in our forwards.
“Yesterday we had good sensations and we managed to overcome difficult moments. We're confident and we'll be going out to beat Iran. We're 100 per cent ready for the game.”