The hosts were conquered 3-1 by group leaders Portugal on matchday three, while the 2018 World Cup finalists came from behind to sink Scotland 2-1 and remain in control of their knockout destiny.
Match preview
Attempting to get the better of Roberto Martinez's Portugal juggernaut proved too tall an order for Poland on Saturday evening, where Bernardo Silva and Cristiano Ronaldo propelled the Selecao into a two-goal advantage before the half-time whistle sounded.
Piotr Zielinski cut the arrears in half late on, ostensibly setting up a tense finale, only for Jan Bednarek to turn the ball past his own goalkeeper and restore Portugal's two-goal cushion in the dying embers of that loss, Poland's fourth from their last six matches.
Coming up trumps in a five-goal thriller with Scotland was initially the perfect tonic to their early Euros group-stage exit, but having now been bested by Croatia and Portugal in back-to-back games, the Eagles are now languishing in third place in the section.
Such a ranking would force Michal Probierz's side to try to salvage their League A status via the relegation/promotion playoffs in the spring, but Scotland only have a three-point gap to make up to Poland, who are at serious risk of a first-ever relegation from the first tier of the Nations League.
The Eagles have also been beaten in each of their last three home matches in the competition, netting just one goal in the process, although they were against three European heavyweights in Portugal, Belgium and the Netherlands.
As Poland were left to rue what could have been against Ronaldo and co, Croatia ensured that Ryan Christie's opener for Scotland in Zagreb would prove inconsequential in the grand scheme of things, as Zlatko Dalic's men fought back to leave Steve Clarke's men still searching for their first point in the section.
Igor Matanovic and Andrej Kramaric had the required response to Christie's opener before Che Adams momentarily thought that he had restored parity for the visitors, only for the VAR room to deny the Torino forward and leave Croatia able to revel in back-to-back Nations League wins.
Aiming to replicate or better last year's run to the final - where Spain denied them a long-awaited international title - the Chequered Ones are currently on course for quarter-final qualification in second spot, three points behind perfect Portugal.
From losing each of their first five Nations League matches that were played outside of Croatia, the 2018 World Cup finalists have now prevailed in four of the last five to have taken place outside of their homeland, the outlier being their narrow loss to Portugal just over a month ago.
However, Croatia immediately responded to that setback with victory over Poland by a goal to nil - Luka Modric was responsible for the winner that day to make it four victories from six for the Chequered Ones against the Eagles, whose only success in this battle came in a 2006 friendly.
Poland Nations League form:
W
L
L
Poland form (all competitions):
L
L
D
W
L
L
Croatia Nations League form:
L
W
W
Croatia form (all competitions):
L
D
D
L
W
W
Team News
Poland lost the trio of Bartlomiej Dragowski, Mateusz Skrzypczak and Kacper Kozlowski prior to their beating at the hands of Portugal, where defender Sebastian Walukiewicz was taken off at the half-time interval.
However, that change may have been tactical in nature from Probierz given that he had picked up a yellow card right on the stroke of the whistle; either way, Arsenal's Jakub Kiwior is a viable alternative.
Top appearance maker and goalscorer Robert Lewandowski could not add to his 84 strikes for the national team on Saturday, but the Barcelona hotshot will certainly reprise his role in attack on Tuesday, potentially with a new partner in Krzysztof Piatek.
As for visitors Croatia, Manchester City lynchpin Mateo Kovacic was not seen against Scotland due to the birth of his child, although Dalic is hopeful that he will be able to take part in Tuesday's contest.
Mario Pasalic was given the nod alongside the evergreen Modric at the weekend, but the Atalanta BC midfielder was hooked at half time, so Kovacic will likely be called upon to replace his fellow ex-Chelsea man if he is back in time.
Whether Modric is able to start two matches in quick succession is another question, though - the 39-year-old completed the full 90 minutes on Saturday and might be due a rest.
Poland possible starting lineup:
Skorupski; Dawidowicz, Bednarek, Kiwior; Frankowski, Zielinski, Szymanski, Urbanski, Zalewski; Piatek, Lewandowski
Croatia possible starting lineup:
Livakovic; Gvardiol, Caleta-Car, Sutalo; Perisic, Modric, Kovacic, Sosa; Sucic, Matanovic, Kramaric
We say: Poland 1-1 Croatia
Lewandowski cannot do it all on his own for Poland, who have failed to pull up trees for a number of months now, although Croatia were fortunate to come away with all of the spoils against Scotland.