After scores remained goalless at the end of 120 minutes in the FIFA World Cup clash, Dutch coach Louis van Gaal surprisingly replaced number one goalkeeper Jasper Cillessen with Krul in Salvador.
Van Gaal's switch proved to be a masterstroke, with Krul saving two penalties as the Netherlands prevailed 4-3 in the shootout to book a last-four showdown against Argentina.
Speaking post-game, Krul said he had practiced alongside goalkeeper coach Frans Hoek for the likely situation of penalties.
"This is what you work for, for seven weeks," the Newcastle United glovesman told reporters.
"Now you can see, you have to do this with all 23 men.
"We had looked at them, but we didn't learn anything. The power was standing still and then going in. Me and Frans Hoek worked on it."
Meanwhile, the Netherlands captain Robin van Persie heaped praise on Krul and Van Gaal, who decided to withdraw Cillessen despite keeping a clean sheet throughout the 120 minutes at the Itaipava Arena Fonte Nova.
"We know that Krul is good at stopping penalty kicks," he said. "The fact that the coach has figured this is fantastic."
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