The Newcastle goalkeeper was introduced in place of Jasper Cillessen in the 121st minute against Costa Rica in Salvador in an extraordinary move by Louis van Gaal.
But, with Cillessen having never saved a penalty in his career, the coach’s decision was justified when Krul saved efforts from Bryan Ruiz and Michael Umana in a 4-3 shoot-out win.
And the 26-year-old told NOS that he had been told the dramatic substitution may materialise before the game.
"I knew there was a chance I would come on if we still had a substitution left. I already started to get a bit anxious toward the end of the game. That things panned out like this is like a dream come true. You can’t understand what I went through,” Krul said.
Cillessen appeared upset after the substitution, but Krul was quick to pay tribute to the starting keeper, picking out a late stop from Marcos Urena’s shot as a key moment in the triumph.
“If Jasper hadn't made that save in the dying seconds we would not even have had penalties,” he added.
“It's fantastic how we are really acting as a team. We looked at their penalties [against Greece], but didn't really learn anything from it. It's all about waiting as long as possible and we trained on that with [goalkeeping coach] Frans Hoek.”
The victory sees the Dutch progress to the last four, where they will meet Argentina in Sao Paulo on Wednesday.