Portugal can not afford to drop many more points as they try to qualify for the 2018 World Cup, coach Fernando Santos said after his side beat the Faroe Islands on Monday.
It was a successful international break for Portugal, with wins of identical 6-0 scorelines against Andorra and the Faroes.
But remembering the 2-0 defeat to Switzerland last month, Santos cautioned that there are still bigger tests to come.
"We've not won more than three points [against the Faroe Islands]," he told reporters. "We have to depend only on ourselves.
"The margin for error is not big. We have to win our remaining games.
"Other teams will not lose many points. If we do not [lose] then I believe that we will finish first."
Andre Silva's early hat trick put Portugal in control before more goals from Cristiano Ronaldo, Joao Moutinho and Joao Cancelo.
Santos said he was satisfied with his side's comprehensive win over the Faroes, from whom he had seen superior performances in the past.
"They fulfilled the plan that we set out with a very correct attitude which was key to the game," he said. "I saw their last two games and today it seemed that it was easy for us.
"Against Hungary and Latvia this team showed quality, but today our attitude was right.
"We were favourites and with the right attitude we lived up to expectations. They took it [the expectations and pressure] in a fantastic way."