Coach Fernando Santos is thrilled his players made the most of their opportunities to grasp a 3-1 lead but has urged focus heading into the second leg.
Two goals from Kostantinos Mitroglou either side of a Dimitris Salpingidis strike ensured the Euro 2004 champions take the advantage heading into the second leg, despite Bogdan Stancu's away goal.
The Portuguese coach is pleased his charges were able to make the most of their chances to score but warned them not to think that a place in Brazil is assured.
"Nothing is decided yet," the 59-year-old said to gathered media after the game. "We need to keep a cool head. Everything will be decided Tuesday. We have the advantage after the win, but we are only halfway through."
Preperations for the decisive match will continue in earnest, Santos said.
"The players have worked hard and took advantage of the opportunities we had. We hope to do the same during Tuesday's game," he said. "In the coming days we will be able to release some pressure. Beyond that, we will prepare properly for the next game."
In the other World Cup playoffs Friday, France was beaten 2-0 in Ukraine, Iceland held Croatia to a home 0-0 draw, and Portugal left it late to beat Sweden 1-0 at Estadio da Luz.