The first leg between the Bulgarian and Swiss sides ended in a goalless draw, keeping the tie in the balance as they bid to make a rare appearance in the latter stages of a continental competition.
Match preview
While Ludogorets are very much regulars on the European scene, they are yet to make the breakthrough when it comes to reaching the last 16 of a tournament.
However, they are just one home win away from achieving that feat having earned a credible goalless draw in Switzerland last week, extending their unbeaten run in this competition to four games in the process.
Having conceded 10 goals in away defeats to Nordsjaelland and Fenerbahce before the end of October, Ludogorets have bounced back impressively to reach this stage.
Georgi Dermendzhiev's side came through the group phase with three wins at their home ground, scoring seven goals without conceding, and it makes them considerable favourites to progress.
That particularly rings true having defeated title rivals Cherno more by a 3-1 scoreline on Monday night, taking them to the top of the domestic standings.
From Servette's perspective, you have to go all the way back to the 2001-02 UEFA Cup for the last time that they went deep in a European competition.
Dropping down from the Europa League after a third-placed finish may prove to be a blessing in disguise on that front, even after holding Roma to a draw in the first half of the season.
Nevertheless, despite sitting in second spot in the Swiss top flight, Servette was underdogs to progress, Rene Weiler's side having not been convincing of late.
Either side of the goalless draw in the first leg, a 2-1 defeat came at the hands of Yverdon Sport before they responded by defeating Lugano by the same scoreline at the weekend.
Ludogorets Razgrad Europa Conference League form:
L
L
W
W
W
D
Ludogorets Razgrad form (all competitions):
Servette Europa Conference League form:
D
Servette form (all competitions):
W
W
W
L
D
W
Team News
Although Bernard Tekpetey was withdrawn during the closing stages a week ago with a knock, he recovered to come through 86 minutes against Cherno More.
Despite the quick turnaround, the team from that fixture could look similar to the one named on Thursday, with winger Caio Vidal missing out after starting the first leg.
Weiler made a number of changes to the Servette XI for their weekend fixture, including goalkeeper Jeremy Frick dropping down to the substitutes' bench.
The 30-year-old should return to the fold for this game, but Alexis Antunes and Dereck Kutesa will hope to keep their spots in the final third.
That would see former Wolverhampton Wanderers man Bendeguz Bolla stay among the replacements, despite making 27 appearances this campaign.
Ludogorets Razgrad possible starting lineup:
Padt; Witry, Verdon, Sundberg, Son; Pedro Nare, Goncalves; Tekpetey, Piotrowski, Rick; Duah
Servette possible starting lineup:
Frick; Tsunemoto, Rouiller, Severin, Mazikou; Stevanovic, Ondoua, Magnin, Kutesa; Antunes; Guillemenot
We say: Ludogorets Razgrad 2-1 (Ludogorets Razgrad to win 2-1 on aggregate) Servette
This has all the makings of a contest that could go either way, Servette more than capable of halting Ludogorets' impressive run in Europe. Nevertheless, we are backing the Bulgarian side to make full use of home advantage, potentially through scoring a late goal to secure their progress.