The Selecao have already confirmed their spot in the quarter-finals as group winners, but their hosts need a point to be absolutely sure of a position in the knockout stages.
Match preview
Still rewriting the history books at the age of 39, Portugal talisman Cristiano Ronaldo was responsible for two of the Selecao's five goals in Friday's 5-1 dismantling of Poland, including an acrobatic overhead kick to bring up his 132nd win on the international stage.
No male player has been involved in more victories for their country than Ronaldo, who left 131-win Sergio Ramos in his wake on November 15, where Rafael Leao, Bruno Fernandes and Pedro Neto also struck before Dominik Marczuk at least managed to wipe out Portugal's clean sheet.
Roberto Martinez and co will not be losing sleep at their failure to secure a shut-out on Friday, though, as they have swept aside the Group 1 competition in customary fashion and have already booked their spot in the quarter-finals as section winners.
Basement boys Scotland are the only team to have taken points off of the 2016 European champions in the current edition, and from the Selecao's previous 10 Nations League matches away from home, only one of them has ended in defeat.
That reverse came at the hands of Switzerland in June 2022, and not since June of this year have Martinez's men conceded more than one goal in a competitive or non-competitive fixture, although there will be no prizes for guessing who that came against.
Indeed, Croatia warmed up for an ultimately disappointing Euro 2024 run with a 2-1 success over Portugal in a summer friendly, but Martinez's men avenged that loss by the same scoreline in their first Nations League showdown of the year back in September, where Ronaldo bagged his 900th career goal.
Results for Zlatko Dalic's side since then have been mixed to say the least, as after taking seven points from nine on offer between September 8 and October 15, the Chequered Ones squandered an opportunity to rubber-stamp a second-placed finish in Glasgow.
Following 85 scoreless minutes at Hampden Park, Aston Villa midfielder John McGinn came up with the telling contribution in a 1-0 success for Scotland, who are therefore still capable of usurping Croatia and nabbing the final qualification spot if Dalic's men lose on Monday.
The 2018 World Cup runners-up hold a three-point lead over both Scotland and Poland, but their superior head-to-head record over the latter means that they cannot be relegated automatically, and just one point in Split will eradicate any doubt over their knockout status.
Croatia's result will also pale into insignificance if Poland beat Scotland or if there is no victor in the other Group 1 battle, and September's loss to Portugal was their seventh defeat from nine previous battles against the Euro 2016 winners, but the visitors may not go gung-ho in their bid to make that eight from 10.
Croatia Nations League form:
L
W
W
D
L
Croatia form (all competitions):
D
L
W
W
D
L
Portugal Nations League form:
W
W
W
D
W
Portugal form (all competitions):
L
W
W
W
D
W
Team News
With top spot in the group already signed, sealed and delivered, Martinez has allowed some of his big-hitters in Ronaldo, Bernardo Silva, Neto and Fernandes - who is suspended for Monday's game anyway - to head back to their clubs early, a huge boost for Manchester United, Manchester City and Chelsea.
To plug the gaps, Martinez has promoted Fabio Silva and in-demand Sporting Lisbon full-back Geovany Quenda up from the Under-21s, and Tiago Djalo is expected to be involved too, having been the unfortunate man to miss out on the 23-player squad against Poland.
Sure to make an abundance of changes for Monday's game, the Portugal boss could introduce the likes of Joao Felix, Joao Cancelo and Vitinha into the Portugal XI, while Rui Silva and Jose Sa will battle to displace Diogo Costa in goal.
Similarly to Fernandes and Portugal, Croatia's own number 10 in Petar Sucic is suspended for Monday's match after being sent off for two bookable offences in the loss to Scotland; either Mario Pasalic or Nikola Vlasic should replace him here.
On two brighter notes, Ante Budimir and first-choice goalkeeper Dominik Livakovic are back from their own bans, and the latter is sure to displace Dominik Kotarski in between the posts, but Andrej Kramaric should hold his place in the final third over Budimir.
An enforced change might have to occur in defence too, as Kristijan Jakic came off with an injury in the dying embers of the loss to Scotland, so Marin Pongracic may be shoe-horned into a right-back role.
Croatia possible starting lineup:
Livakovic; Pongracic, Caleta-Car, Sutalo, Gvardiol; Modric, Kovacic; L. Sucic, Pasalic, Perisic; Kramaric
Portugal possible starting lineup:
R. Silva; Cancelo, Djalo, Araujo, Tavares; Vitinha, Neves; Conceicao, Felix, Trincao; F. Silva
We say: Croatia 1-1 Portugal
With Martinez already sending a few world-class troops home, and Portugal having nothing but personal pride on the line, it would not be surprising to see a hint of complacency creep into the visitors' game.