Fernando Santos's side currently occupy second place in League A Group 2 - one point below Spain - while their hosts sit third as they aim to preserve their top-flight status.
Match preview
Following their failure to make it past Sweden in the qualifying playoffs for the 2022 World Cup, the Czech Republic will be finished with competitive action at the end of the month, and a first appearance on the biggest stage of them all since 2006 still eludes them.
The foundations are certainly there for Jaroslav Silhavy's side with Adam Hlozek and Patrik Schick among their attacking options, and their start to life in Nations League A has been a solid, if yet unspectacular affair.
The Czech Republic have accumulated four points from their opening four games to sit third in the section - one point clear of Switzerland in the relegation spot - and it is still not impossible for Silhavy's side to secure an unlikely place in the finals.
However, this week's hosts ended the month of June with back-to-back 2-0 defeats to upcoming opponents Portugal and Spain, with Carlos Soler and Pablo Sarabia on target for the latter, and it is now six games without a clean sheet in all tournaments for the Czechs.
On a brighter note, Silhavy's side have never failed to score at home in the UEFA Nations League and have gone unbeaten in their last four such matches - winning three of them - but Portugal will prove a different kettle of fish than their League B opponents.
While their Iberian neighbours were busy getting the better of the Czech Republic, Portugal ceded their place at the top of the League A Group 2 rankings to La Roja, as they went down 1-0 to Switzerland in their most recent encounter.
Haris Seferovic took just 57 seconds to head home the decisive goal to end Portugal's hopes of three consecutive wins from their first three Nations League encounters, as well as ending a five-game unbeaten run in all tournaments for the 2018-19 champions.
Having been forced to get the better of North Macedonia in the World Cup playoff route, Santos's men are now preparing for battle with Uruguay, Ghana and the Korea Republic in Group H, but their Nations League fate could be sealed here.
Defeat for Portugal coupled with victory for Spain at home to Switzerland would see Luis Enrique's men make the finals, as Santos aims to end his side's three-game winless streak on the road in all tournaments during their maiden visit to Prague.
Joao Cancelo and Goncalo Guedes were on target when the Selecao saw off their Czech counterparts 2-0 three months ago, which marked Portugal's third consecutive win over Saturday's hosts, having previously only met at the Euros.
Czech Republic form (all competitions):
W
D
W
D
L
L
Portugal form (all competitions):
W
W
D
W
W
L
Team News
The Czech Republic will welcome Bayer Leverkusen striker Schick back to the fold with open arms this week, as the 26-year-old returns to the squad for the first time in over six months following his comeback from injury.
Slavia Prague midfielder Petr Sevcik is reportedly dealing with an illness and will need assessing ahead of the contest, while fellow engine room member Michal Sadilek has not been called up owing to a hamstring injury.
West Ham United's Tomas Soucek could therefore link arms with ex-Hammer Alex Kral in the midfield, while Tomas Vaclik should regain his place in goal over Ales Mandous.
Meanwhile, Portugal full-back Cancelo will not get the opportunity to build on his goal over the Czechs back in June here, as he picked up his second yellow card of the tournament against Switzerland and is therefore suspended.
Santos should therefore hand a start to Diogo Dalot on the right-hand side following his Manchester United revival, but fellow defenders Pepe and Raphael Guerreiro have both withdrawn due to injury alongside Rafa Silva, who has retired from international duty at the age of 29.
Joao Felix was training individually earlier this week and may not come into Santos's thinking for a starting role, with Cristiano Ronaldo instead in line to win his 190th cap for the Selecao.
Czech Republic possible starting lineup:
Vaclik; Zima, Brabec, Jemelka; Coufal, Kral, Soucek, Zeleny; Cerny, Schick, Hlozek
Portugal possible starting lineup:
Patricio; Dalot, Dias, Pereira, Mendes; Neves, Carvalho, Fernandes; B. Silva, Ronaldo, Leao
We say: Czech Republic 0-1 Portugal
Despite their defensive absentees, Portugal can still field a menacing-looking rearguard, and Santos's side should win the midfield battle with ease given the hosts' woes in that area.