A win over Luxembourg on matchday eight has put the hosts on the brink of a third successive finals appearance, taking them five points clear in the group.
Match preview
Slovakia's buffer in second place means that even a defeat here will keep their fate in their own hands before facing already-eliminated Bosnia-Herzegovina on the final matchday.
For Iceland to keep themselves in contention, they must win this match by any scoreline except 1-0, because a 2-1 win for Slovakia in the reverse means they would still have the edge on head-to-head with three points separating the sides.
If Iceland win 2-1, they will have the upper hand on goal difference, while a win of any other scoreline would give them the ascendancy in the head-to-head record.
However, they would need Slovakia to lose in Bosnia, Luxembourg to drop points, as well as picking up a win themselves, away to a Portugal side who have won every game so far in the section.
It looks far-fetched and it is incredibly unlikely, but Iceland will at least have a playoff place to fall back on thanks to their performance in the last Nations League campaign.
It leaves Slovakia as the overwhelming favourites to join Portugal in the finals from this section, as they also have a favourable head-to-head record over Luxembourg thanks to their matchday eight victory.
Francesco Calzona's side have been good in the section and deserve their place in the finals as they have proven so far that they are the best of the rest in the group, as apart from a matchday one draw with Luxembourg, only Portugal have taken points off them.
With Milan Skriniar and David Hancko at the back and Napoli maestro Stanislav Lobotka in front, Slovakia's foundations have been rooted in defensive solidity, keeping five clean sheets in their eight qualifiers so far.
They are one of the nations who have taken full advantage of the Euro's expansion to 24 teams, as this will be a third qualification from three since the number of teams was increased for Euro 2016, having not reached a single finals prior following independence from Czechoslovakia in 1992.
Their fairytale run at Euro 2016 and a respectable showing at Russia 2018 remain Iceland's only moments in limelight, and they will have to hope they can navigate the playoffs if they want a taste of major tournament football again, unless a remarkable set of results transpire in this section.
After losing four of their first five games in Group J, Iceland looked dead and buried, but a late surge has still given them minor hope of a miraculous automatic qualification.
Hopes certainly looked like they had diminished when beaten by Luxembourg in September, but they have taken seven points from a possible nine since then, meaning it is still mathematically possible.
Age Hareide's men were extremely fortunate in their reverse tie with Luxembourg last month though, as their opponents missed a clear open goal to win the game with the last kick when Iceland sent goalkeeper Alex Runarsson up for a corner with the score at 1-1.
That could suggest fate is on their side, but it is a very daunting fixture to finish with though, away to Portugal, even if they did hold out for 89 minutes in Reykjavik before a late Cristiano Ronaldo winner earlier in the group.
Slovakia Euro Champ Qualifying form:
W
W
L
W
L
W
Iceland Euro Champ Qualifying form:
L
L
L
W
D
W
Advert - content below:
Team News
Slovakia have been boosted massively by the return of Sparta Prague winger Lukas Haraslin, who missed October's internationals with injury.
Matus Bero and Adam Zrelak are the most notable Slovak absentees due to injury, but that has given the opportunity to 17-year-old Leo Sauer to come in, after the Feyenoord youngster scored on his professional debut earlier this season.
Robert Bozenik is still in form at Boavista, but he is battling for a starting spot up front with namesake Robert Polievka.
Veteran right-back Peter Pekarik is on course to reach 125 caps if he features in both internationals for Slovakia during this break.
Danish-based duo Gylfi Sigurdsson and Mikael Anderson have both withdrawn from the Iceland squad due to injury, with Andri Gudjohnsen and Mikael Egill Ellertsson replacing them.
Sigurdsson made his first Iceland appearances in over three years last month, scoring twice against Liechtenstein, but he missed Lyngby's clash with Vejle last weekend and has been ruled out here.
Defender Hordur Magnusson remains out injured, but there is a place for Kristian Hlynsson, who has been rewarded with another call-up after being one of the rare bright sparks for Ajax this season, in particular, scoring two in defeat to Utrecht.
Slovakia possible starting lineup:
Dubravka; Pekarik, Vavro, Skriniar, Hancko; Duda, Lobotka, Kucka; Schranz, Bozenik, Haraslin
Iceland possible starting lineup:
Runarsson; Sampsted, Palsson, Ingason, Finnsson; Willumsson, Traustason, Haraldsson; Gudmundsson, Oskarsson, A Sigurdsson
We say: Slovakia 2-0 Iceland
Slovakia's 2-1 win in June was the first-ever competitive meeting between the nations, and back on home soil, the hosts will expect another result to confirm their place at the finals.