The 32-year-old Barcelona captain has made a smooth transition from an attacking role to central midfield and been instrumental in his country's two victories over the Czech Republic and Turkey in Group D.
"For a midfielder like me, the most important thing has been, is and will be to think fast," Iniesta told El Mundo newspaper on Tuesday. "Certain things occur automatically, but to think fast is the only secret."
The holders, who top the group ahead of their final group clash with Croatia on Tuesday, have greatly benefitted from Iniesta's form over the years and, despite a change of position, the player has thrived.
"Before he had a more attacking role and now he has taken a midfield position which suits him," Spain coach Vicente del Bosque said.
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"He has a lot of security and a good physical condition which makes it easier for him to have better coordination in what he does."
Since making his debut with the senior side a decade ago, Iniesta has made 111 appearances. The Barcelona captain played in Spain's title-winning sides at the European Championships in 2008 and 2012, and at the 2010 World Cup.
His finest moment was his extra-time goal against the Netherlands six years ago to hand Spain their first world crown. But the midfielder is keen to stress that he is just part of a team.
"Everyone adds, no player can win a game on his own," he said. "I've always interpreted football as a collective game and assume my quota of responsibility. Each of us has to be the best in his position to win.
"As time goes by, you receive more praise but I still view myself in the same way. I am nothing without my team mates. We are growing in the tournament. We need to maximize the good things we do and limit mistakes."
(Reporting by Adriana Garcia. Editing by Adrian Warner.)
