The Irish side went down 5-1 in the opening fixture in Norway, with a complete capitulation being required from the visitors to change the course of this tie.
Match preview
Having posted two famous victories over Motherwell in the previous round, Sligo Rovers would have been dreaming of building on those achievements in the latter stages of qualifying.
However, conceding twice in the opening eight minutes in Norway started the process of this tie turning into a nightmare, the visitors finding themselves four goals adrift by the hour mark.
John Russell's side scored a consolation goal from the penalty spot in the closing stages, but there will be an acceptance that this tie is probably already over.
That is not to say that Sligo Rovers will not want to go out on their shield after providing their supporters with some unforgettable memories over the course of the last few weeks.
Russell will also want to generate some momentum on the back of the comeback 2-1 triumph over Bohemians at the weekend, keeping the club in fifth position in the League Of Ireland Premier Division.
Viking, without a league title since 2018, have taken people by surprise in the early rounds of this competition, the expectation having initially been that they would lose out to Sparta Prague.
However, they proved last week that they have the quality to earn a spot in the group stages and ensure that few teams would want to play them home and away.
Their domestic campaign has not been going to plan, a 2-2 draw at eighth-placed Sandefjord leaving the club in fifth position, 13 points adrift of leaders Molde.
Nevertheless, retaining their participation in this tournament would enhance the reputation of Viking, who may already have one eye on facing either FC DAC 1904 or FCSB in the playoff round.
Sligo Rovers Europa Conference League form:
Sligo Rovers form (all competitions):
Viking FK Europa Conference League form:
Viking FK form (all competitions):
Team News
Having netted twice as a substitute at the weekend, Max Mata will hope to earn a recall to the Sligo Rovers attack.
However, Adam McDonnell and Garry Buckley appear likely to miss out after both were withdrawn inside 22 minutes against Bohemians.
Nando Pijnaker is also in line to get another opportunity in the centre of the defence.
Meanwhile, Viking may line up with a similar team to the first leg, particularly with changes having been made for the weekend.
Daniel Seland Karlsbakk could return in attack with Mai Traore having failed to get on the scoresheet in his place on Sunday.
Sligo Rovers possible starting lineup:
McNicholas; Buckley, Pijanker, Kirk, Blaney, Cawley, Mata, Morahan, Keena, Fitzgerald, O'Sullivan
Viking FK possible starting lineup:
Gunnarsson; Vevatne, Bjorshol, Brekalo, Pattynama, Tripic, Fridjonsson, Tangen, Solbakken, Kabran, Karlsbakk
We say: Sligo Rovers 1-4 Viking FK (Viking FK to win 9-2 on aggregate)
While everyone associated with Sligo Rovers may be prepared to accept achieving some respectability, the players will feel inclined to push for victory. However, Viking have already showcased their greater class, and we expect to see more of the same on Thursday.