The hosts, meanwhile, claimed a respectable 0-0 draw away to Slovakia in their opening match in Group J.
Match preview
Indeed, Luxembourg displayed their continued improvement in recent years by extending their unbeaten run to six matches in all competitions in Trnava on Thursday.
The hosts generated 18 shots across the course of the 90 minutes, but only managed to test Luxembourg's goalkeeper Anthony Moris on three occasions, as the Union SG stopper stood firm and kept his third clean sheet in his last four international outings.
With second spot in Group J looking wide-open - if we are to assume favourites Portugal are likely to run away with things - it was crucial for Luxembourg to avoid defeat in their first match as they look to qualify for a major tournament for the first time in their history.
Having won three of eight matches in the most recent World Cup qualifying campaign to finish level on points with third-placed Republic of Ireland, Luc Holtz and his players will firmly believe that they can push for a top three place, with the likes of Slovakia, Iceland and Bosnia & Herzegovina providing no fear factor for them.
However, claiming a positive result against Portugal on Sunday will be the ultimate litmus test for The Red Lions, especially having been beaten by them in both matches in the aforementioned qualifiers for Qatar.
After winning their opening two matches at the recent World Cup before thrashing Switzerland 6-1 in the last-16 to reach the quarter-finals for only the third time in their history, Portugal looked capable of going all of the way in Qatar.
However, they were stunned 1-0 by Morocco in the last eight as Youssef En-Nesyri's 42nd-minute header proved enough for the north Africans to make history as the first ever nation from that continent to reach the semi-finals of international football's most prestigious tournament.
Roberto Martinez has since left his managerial post at Belgium to replace Fernando Santos in Portugal's dugout, ending Santos' eight-year reign in charge of his home country. Having guided them to their first ever major tournament triumph at Euro 2016 before winning the inaugural UEFA Nations League three years later, Santos will remain a legendary figure in his homeland despite suffering subsequent disappointments.
Martinez has likely been appointed in an attempt to bring more attractive football to A Seleção, with Santos' style generally regarded as being too conservative at times.
The likes of Joao Felix and Rafael Leao represent a new era of exciting Portuguese football, although Cristiano Ronaldo is still clinging onto his place in attack despite moving to Saudi Arabia in the club game. The 38-year-old scored twice as Portugal thumped Liechtenstein 4-0 in Martinez's first game in charge on Thursday.
The former Everton boss will now be desperate to lay down a marker by making it two wins from two, but he will be acutely aware that the trip to Luxembourg is likely to provide him and his new set of players a much stiffer challenge, even if they will be expected to prevail comfortably in the end.
Luxembourg Euro Champ Qualifying form:
D
Luxembourg form (all competitions):
L
D
D
W
D
D
Portugal Euro Champ Qualifying form:
W
Portugal form (all competitions):
W
W
W
L
W
L
Team News
Having fought hard to claim a positive result in Slovakia on Thursday, Holtz is unlikely to make any changes to his starting XI against Portugal, meaning Lars Gerson should hold onto his starting berth in defence alongside Maxime Chanot.
Captain Laurent Jans was surprisingly only used from the bench during the 0-0 stalemate, with Florian Bohnert preferred at right-back, while the likes of Daniel Sinani, Yvandro Borges Sanches and Mathias Olesen will be tasked with ensuring that Portuguese-born Gerson Rodrigues does not end up becoming isolated in attack.
Martinez, meanwhile, utilised a 3-5-2 system in his first match in charge against Liechtenstein, having generally used that formation throughout his time in charge of Belgium.
Although the likes of Leao, Ruben Neves and Goncalo Ramos showcased Portugal's tremendous strength in depth by appearing as second half substitutes in Lisbon, Martinez may choose to choose the same team on Sunday, with Bruno Fernandes and Bernardo Silva supporting Ronaldo and Felix in a fearsome central box.
Luxembourg possible starting lineup:
Moris; Bohnert, Chanot, Gerson, Pinto; Sinani, Barreiro, Pereira, Olesen, Sanches; Rodrigues
Portugal possible starting lineup:
Patricio; Danilo, Dias, Inacio; Cancelo, Silva, Palhinha, Fernandes, Guerreiro; Ronaldo, Felix
We say: Luxembourg 0-2 Portugal
Although Luxembourg have clearly dramatically improved during Holtz's lengthy spell in charge of his home nation, they are still someway short of being able to consistently challenge against teams of Portugal's calibre.
Martinez's secondary aim from the trip to Luxembourg City may be keeping another clean sheet, and we can envisage a tighter victory than many may expect as a result.