While Porto are playing their first fixture at the third-round stage, Estoril have already posted a victory over Leixoes.
At a time when they only sit in third position in Primeira Liga and are yet to qualify for the Champions League last 16, this is an important stage of the season for Porto.
Their most recent form has generally been impressive, winning a total of eight of their last 10 fixtures in all competitions and keeping six clean sheets during that period.
Nevertheless, they succumbed to a 2-1 defeat in Barcelona last week having previously held the lead, while Sergio Conceicao watched Porto lose 1-0 at home to their upcoming opponents in the league on November 3.
On a positive note, a 3-0 triumph was registered at Familicao on Saturday, a result that has moved them to within top spot after Benfica dropped points and with Sporting Lisbon not playing until Monday.
With crucial games against Shakhtar Donetsk and Sporting coming up in due course, Conceicao will want to build momentum ahead of that crucial double-header.
From Estoril's perspective, participating in this competition is a welcome distraction to trying to avoid dropping into the relegation zone on a weekly basis.
The bottom seven teams in Portugal's top flight are separated by just three points, Estoril fifth from bottom having managed to post two wins in their last three league outings.
As well as the aforementioned triumph over Porto at Estadio do Dragao, Estoril thrashed Casa Pia by a 4-0 scoreline before losing out 3-1 at Braga last time out.
Estoril's Taca da Liga hopes have been boosted by a 2-1 success over Leixoes, putting them in a position where victory on Wednesday will secure a place in the last four and eliminate Porto in the process.
Given the magnitude of the game, head coach Vasco Seabra could opt for his strongest lineup, with that being the one from Sunday after Estoril initially led at the title challengers.
Despite having made his first outing from the bench in three months at the weekend, defender Raul Parra is unlikely to be considered for a start at this stage.
Conceicao may take a different approach with his Porto side given their upcoming schedule and the likelihood is that several alterations will be made.
Estoril Praia possible starting lineup:
Carnes; Feltes, Alvaro, Vital; Pina, Holsgrove, Fernandes, Araujo; Guitane, J. Marques; A. Marques
Porto possible starting lineup:
Costa; Sanchez, Carmo, Cardoso, Sanusi; Aquino, Varela, Grujic, Galeno; Evanilson, Martinez
We say: Estoril Praia 0-2 Porto
Despite already having a win under their belts, Estoril will recognise that they will probably have to win this fixture in order to progress. That may play into Porto's hands and we feel that the visitors should be able to record a hard-earned victory.
For data analysis of the most likely results, scorelines and more for this match please click here.
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