Classy Portugal midfield finds way through
Carlos Queiroz made four changes to the side that started in the goalless draw with the Ivory Coast, one of them forced, the others designed to spur his side into scoring.
The coach has been criticised for his inability to make the team cap fine displays with goals, but on Monday his changes and approach led to Portugal's biggest ever win at World Cup finals.
"It was a great display, good goals, great attitude. We needed a moment like this, a well-played game so that the motivation and confidence can be even bigger now," he said.
Ironically, it was the substitution he was forced to make with Deco's hip injury that worked best. Tiago was involved in everything Portugal did well.
His toe-poke through ball for Meireles' opener eliminated four players from the move, proving he can fill Deco's boots.
He was also involved in Portugal's third, feeding the lively Fabio Coentrao, and grabbed two himself as Portugal ran riot.
Meireles' instinct for moving into space for his opener was seen again several times as he roamed the North Korean half at will. His touch to Simao Sabrosa - another change, starting instead of Danny - for the second made it easy for the winger.
Until Meireles opener, a thumping looked unlikely as the North Koreans withstood a powerful first 10 minutes from Portugal to balance the game out and give Eduardo a few scares.
In that period, and again to Queiroz's credit, right back Miguel showed more resilience than Paulo Ferreira had last week.
But once Portugal claimed their first, it became clear Queiroz's instructions has been followed - score, secure the win and then make qualification almost certain with a rout.
Their midfielders' control later allowed the forwards to exercise their scoring skills. Hugo Almeida, another change in the eleven, headed in and Liedson scored just after coming on.
Ronaldo cannot have imagined that his "ketchup" goals would start flowing with a goal that hit the back of his neck before falling for him, but he will certainly not complain.
Portugal will take heart from his performance, his constant shooting hitting the bar, the keeper or going just wide.
The rout gives Portugal a goal count that will almost surely take them to the next round even if they lose to Brazil. But with their midfield flowing smoothly and Ronaldo back in form they will fancy their chances of beating the Brazilians.