Meanwhile, the visitors have little to play for after their hopes of finishing top of League A Group 3 were dashed by France on matchday five.
Croatia's 2020-21 Nations League campaign has been a torrid affair for a country who reached the World Cup final two years ago. With only three points taken from a possible 15, Tuesday's hosts are at real risk of dropping down to League B ahead of the final matchday in the group.
Being placed into a group with world champions France and European champions Portugal always promised to be a daunting task for Zlatko Dalic's side, whose solitary victory in League A Group 3 came against Sweden last month.
Croatia could therefore have been forgiven for feeling optimistic about their chances of another victory against a Sweden side who had lost their opening four matches, but Dalic's men became the Swedes' first victims at the weekend as they succumbed to a 2-1 defeat at the Friends Arena.
As things stand, Croatia and Sweden are level on points, head-to-head record and goal difference, with the 2018 World Cup runners-up sitting above Sweden courtesy of a higher number of goals scored, with Dalic's men notching up seven strikes compared to a mere three for their relegation rivals.
Anything other than a victory for Croatia leaves the door open for Sweden to try to climb out of danger, but while Dalic's side are up against it themselves on Tuesday, Sweden are certainly not expected to come away from their encounter with France with something to show for their efforts.
Meanwhile, Portugal's Nations League crown is slowly slipping off. The defending champions have missed out on a place in the finals after suffering a 1-0 defeat to France in their penultimate group game.
The ever-reliable Rui Patricio, who made a number of top-drawer saves on the night, palmed a shot straight at the feet of N'Golo Kante, who made no mistake to send Les Bleus through at the expense of Portugal.
Fernando Santos's men realistically have nothing to play for in their final group match - France are three points ahead and cannot be caught owing to their superior head-to-head record - meaning that the Portugal manager may be tempted to tinker with his lineup on Tuesday.
However, the current champions will no doubt want to go out with a win despite already being guaranteed to finish second, with Santos already sure to have one eye on next year's European Championships as Portugal endeavour to launch a successful defence of that crown.
Croatia Nations League form: LLWLL
Croatia form (all competitions): LWWLDL
Portugal Nations League form: WWDWL
Portugal form (all competitions): WDDWWL
Croatia will be forced into a couple of alterations in defence for this crucial game, with Marseille centre-back Duje Caleta-Car suspended after picking up his second booking of the group phase last time out.
Meanwhile, Portugal have no injury or suspension concerns whatsoever for their trip to Split, but Santos could make a few changes with little on the line and no need to take any unnecessary risks.
Jota, who has been in electric form for Liverpool, could be handed a start, while Wolverhampton Wanderers trio Nelson Semedo, Ruben Neves and Joao Moutinho will all be vying for spots in Santos's first XI.
Croatia possible starting lineup:
Livakovic; Juranovic, Pongracic, Lovren, Barisic; Modric, Kovacic; Brekalo, Vlasic, Perisic; Budimir
Portugal possible starting lineup:
Lopes; N. Semedo, Dias, Duarte, Guerreiro; Pereira, Neves, Fernandes; Trincao, Ronaldo, Jota
We say: Croatia 1-2 Portugal
Croatia have it all to lose in this encounter, whereas Portugal are simply playing for pride. The hosts will name a couple of changes in defence, which could have Cristiano Ronaldo and co licking their lips at the prospect of a few more goals against their midweek opponents. We expect Portugal to recover from their loss to France to take the spoils in this one, but with Sweden facing off against Les Bleus on the same night, we do not expect Croatia to be relegated.