However, if Gibraltar can prevail in Sofia, the minnows of the group would move above their hosts with one game remaining.
Match preview
Although Bulgaria were certainly not clear favourites to prevail from this group, the Lions appeared well set to make a strong challenge for promotion.
That is not how it has turned out with three draws coming from their opening four fixtures, the last of which was a spirited goalless draw against leaders Georgia.
The lack of wins and 5-2 defeat at home to the frontrunners have left Bulgaria with work to do in order to avoid the embarrassment of losing their status at this level to their upcoming opponents.
Gibraltar's comeback 1-1 draw in June represented one of the most notable results in their short history, upping the stakes for Bulgaria who were competing in the second tier of this competition during the previous edition.
Remarkably, Bulgaria have gone 13 matches without recording a victory in this competition, a streak stretching to October 2018, and new head coach Mladen Krstajic knows that the stakes are high heading into this game.
Victory on Friday would leave Bulgaria five points clear of bottom-placed Gibraltar with a match remaining, but the opposite result would leave Gibraltar dreaming of their biggest achievement in international football.
Los Llanis are currently on a 21-match winless streak in all competitions, but holding Bulgaria as recently as three months ago means that spirits are high ahead of this game.
Julio Cesar Ribas's team have only netted once in six outings, that being Liam Walker's penalty in the game in question, but Gibraltar have three draws to their name in six outings.
However, last time out, Gibraltar were thrashed 4-0 in North Macedonia, each of the goals being scored by the 31st minute.
Bulgaria Nations League form:
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Bulgaria form (all competitions):
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Gibraltar Nations League form:
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Gibraltar form (all competitions):
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Team News
Despite Bulgaria earning a solid draw at Georgia last time out, Krstajic has rung the changes to his squad, and half the team will be different to that fixture.
Svetoslav Vutsov, Petko Hristov, Ilia Gruev, Yanis Karabelyov, Kiril Despodov and Georgi Rusev could all be drafted into the starting lineup.
There is a far more familiar look to the Gibraltar squad, but that is not to say that alterations will not be made by Ribas.
Reece Styche may get a run out ahead of Lee Casciaro down the middle of the attack, while Ethan Jolley is an alternative to Scott Wiseman at right-back.
Bulgaria possible starting lineup:
Vutsov; Turitsov, Galabov, Hristov, Nedyalkov; Gruev, Karabelyov; Despodov, Stefanov, Rusov; Michev
Gibraltar possible starting lineup:
Banda; Jolley, Annesley, Lopes, Chipolina, Olivero; Valarino, Torrilla, Britto; Walker; Styche
We say: Bulgaria 2-0 Gibraltar
Having already earned a shock draw against Bulgaria, Gibraltar will be confident of at least repeating that feat on Friday. Nevertheless, the home side should still have enough quality to come through this contest, even if they are made to fight along the way.