From this season, only eight clubs enter the competition, as opposed to the previous iterations which included a group stage and 36 teams.
Match preview
Despite the unpopular decision which saw Sergio Conceicao depart as manager over the summer, new boss Vitor Bruno has made an impressive start, and that continued with a 5-0 thrashing of AVS on the road at the weekend.
That has extended their recent run to five wins in six games - with the only exception being the 3-3 draw with Manchester United in the Europa League, which they arguably also should have won.
A loss to Sporting Lisbon at the end of August remains the only thing separating the two clubs at the top of the Primeira Liga, as Porto have won all of their other eight games in the league so far.
Bruno's men also got back on track in Europe last midweek, beating Hoffenheim 2-0 after dropping five points in their opening two games.
This will be their second domestic cup outing of the season, and is almost certainly set to be a tougher test than the win over Sintrense in the Taca de Portugal, but they will still be big favourites.
A clash with Estoril is also on the horizon at the weekend before two huge games heading into the international break, as Porto will go to Lazio and Benfica in two crucial games over two competitions.
Moreirense provide the first challenge before then, but Porto will be hugely confident having won all previous 14 home games against their upcoming opponents.
The visitors have struggled greatly here recently, with their last 10 defeats seeing them concede 38 goals at the Dragao.
Young manager Cesar Peixoto has picked up where Rui Borges left off last season though, as Moreirense qualified for this competition by sneaking into Portugal's top six last season.
Despite narrowly missing out on Europe, it was still an excellent achievement, and the Green and Whites are backing up those performances again, currently sitting seventh.
A good 2-0 win at Boavista over the weekend keeps them in the hunt for Europe again, sitting just three points off those places at present, despite going five games without a win between late August and late September.
Their only other cup outing so far was slightly underwhelming though, as they limped over the line against third-tier Santarem 2-1, needing to come from behind to win.
The Taca de Liga is the one major trophy Moreirense have won though, doing so against all odds in 2017, beating Porto in the group stage, Benfica in the semi-final and Braga in the final, so the small section of away fans will be dreaming when they head here.
Porto form (all competitions):
W
D
W
W
W
W
Moreirense form (all competitions):
L
D
L
W
W
W
Team News
Zaidu Sanusi continued his recovery from an ACL tear by playing an hour for Porto's B team at the weekend, and is now not too far away from returning to the first team.
The same injury is currently keeping Ivan Marcano out though, and he is still some way from making his comeback in defence.
After being benched at the weekend, Ivan Jaime and Galeno could make starts here, while Fabio Vieira's recent return from a lengthy injury could see him rested.
Caio Secco was the preferred choice in goal when Moreirense faced Santarem in the Portuguese Cup just over a week ago, so could get the nod again over first-choice Kewin.
Apart from that though, Peixoto picked a very strong team for the win over the lower-league outfit, so could opt to keep a similar side to the one that beat Boavista at the weekend.
Portugal Under-21 international Pedro Santos and weekend-goalscorer Gabrielzinho did not start in that away win though, and will be pushing for starts in this one.
Porto possible starting lineup:
Claudio Ramos; Joao Mario, Jose Pedro, Perez, Moura; Varela, Eustaquio, Ivan Jaime; Rodrigo Mora, Fran Navarro, Galeno
Moreirense possible starting lineup:
Caio; Dinis Pinto, Marcelo, Ponck, Frimpong; Ruben Ramos, Ofori; Gabrielzinho, Alan, Pedro Santos; Guilherme Schettine
We say: Porto 4-0 Moreirense
Moreirense have lost on every previous visit to the Dragao, and despite performing miracles in this competition in 2017, which included a win over Porto, a repeat is hugely improbable.