Andre Andre's first-half goal and a late Nani free-kick sealed a narrow 2-0 friendly win for Portugal in Luxembourg, although the hosts had plenty of chances to pull off a shock result.
Andre's strike, a low shot converting Vieirinha's cross, opened the scoring on the half-hour mark, with Lucas Joao guilty of missing two brilliant opportunities to extend the lead.
Luxembourg were full of confidence after pulling off a surprise 1-0 victory against Greece on Friday and battled hard, Stefano Bensi and Aurelien Joachim both going close.
Awful weather made conditions particularly hard in the second half and the home side were denied a late penalty when the ball struck Neto on the arm in the box, but the officials did not think the contact was deliberate.
And Nani sealed the win for Portugal, beating Luxembourg goalkeeper Jonathan Joubert with a low set-piece from the edge of the box three minutes from time.
Portugal coach Fernando Santos named a young team, making 10 changes from the side that lost 1-0 to Russia on Friday night, with only Andre keeping his place. Cristiano Ronaldo was left out of the Portugal squad for these friendlies.
Although Portugal dominated possession in the early stages, Luxembourg had the first clear chance after 12 minutes. Stefano Bensi broke down the right and crossed for Joachim, who shot first time just wide.
Portugal should have taken the lead eight minutes later. After Mario Mutsch was booked for a foul, Joubert flapped at Ruben Neves' free-kick and Neto headed over the crossbar.
Bensi then had a fine chance to open the scoring, but Anthony Lopes saved with his legs and Joachim's shot from the rebound was blocked and another effort from Bensi went just wide.
Andre found Joao with a ball over the top of the Luxembourg defence after 28 minutes, but, after rounding Joubert, his touch was heavy and his shot hit the side netting.
Portugal's mounting pressure, though, did pay off two minutes later when Vieirinha did well down the right and crossed for Andre to shoot low past Joubert.
Luxembourg, 142 places below Portugal in the FIFA rankings, responded strongly and Christopher Martins Pereira fired wide.
Vieirinha came close to doubling his side's lead after 39 minutes with a low free-kick from the edge of the box that curled narrowly wide. Joao then missed a fabulous chance from six yards just before the break, side-footing wide after linking up brilliantly with Rafa Silva.
Both teams struggled for cohesion in the second half as substitutions slowed down the tempo, although Neto went close after 57 minutes.
Heavy rain made conditions difficult with both sides struggling for balance on the slippery pitch. Joachim, Luxembourg's hero against Greece, had a couple of sights of goal, but was unable to make his chances count.
The hosts then saw their penalty appeals against Neto waved away before substitute Nani compounded their frustrations when he stepped up to convert a late free-kick with a fine low finish into the bottom corner.