The European champions extended their unbeaten run to 33 matches with an embarrassingly one-sided win, and were 4-0 up inside 24 minutes with Liverpool striker Fernando Torres grabbing a hat-trick. Cesc Fabregas was also on the scoresheet with David Villa netting a fifth in the mining town of Rustenburg.
But Del Bosque was quick to reject any suggestions his side would now cruise to victory in the competition - which includes world champions Italy, hosts South Africa and Brazil - suggesting tougher tests would lie ahead. "We shouldn't think too much about ourselves after this. We can't think we're the best team because this game was deceptive," he said.
"You have to take into account how the opposition made some things easy for us. We did pretty well in the first half and then there was no need to play the second 45 minutes. We did what we needed to do at the beginning, with plenty of control and movement. In the second half we dropped off a little, but it's normal that the players would regulate their efforts."
Meanwhile Torres vowed to continue making history after netting the fastest hat-trick in the history of the Spanish national side. His strikes over an 11-minute period between the 6th and 17th minute bettered a record which had stood since 1949, and which was equalled just five days ago by Torres' strike partner Villa in a friendly with Azerbaijan.
It was also the quickest hat-trick in FIFA Confederations Cup history, with Torres beating the record set by former Liverpool player Vladimir Smicer in 1997. "This latest achievement is a new reason to be proud. As long as it helps the national team to win games, the players to have confidence and for the fans to take to us then all the better", he said.
"It's a great satisfaction for me to have my name written alongside the greats in Spanish football. Now we need to look forward, and score plenty more goals which will allow me a place in history."
One person not listening to Del Bosque's words of caution however was New Zealand captain Tim Brown, who hailed his opponents as "the best team in the world, no doubt". He added: "At the end of the day we have to put things in perspective.
"We're playing against the best players in the world and you can't afford to have that kind of beginning and you can't afford to give them that amount of space. We have to learn from the mistakes we made and take away some of the positives of the second half because I think there were some."