The home side have a one-goal deficit to make up from the first leg while the visitors seeks to hold on to their narrow advantage from last week's encounter.
Match preview
Zalgiris made it seven league victories on the spin as they saw off the threat of Jonava thanks to a 3-1 victory in their encounter on Sunday evening.
Vladimir Cheburin's men put themselves in cruise control thanks to Renan Oliveira's opener and a second-half double from Josip Tadic before Marius Ganusauskas pulled one back late on.
The Green Whites remain top of the A Lyga standings, two points clear of nearest challengers Hegelmann albeit having played a whopping four games fewer.
The Lithuanian champions now set out to preserve their European ambition as they look to participate in a major continental tournament for the first time ever.
Having won six and drawn one of their most recent seven home involvements, Thursday's will fancy themselves to get the job done and complete a remarkable turnaround.
Ludogorets breezed past the challenge of Pirin Blagoevgrad following a 4-0 victory in the sides' meeting at the Hristo Botev on Monday.
Ante Simundza's men turned on the style in the second period as strikes from Georgi Terziev, Matias Tissera, Jorginho and a Kazuki Takahashi own goal got the job done.
As a result, the Eagles have moved up to third place in the Parva Liga table, four points behind league leaders CSKA Sofia who have however played two extra games.
Off the back of a 1-0 victory against Thursday's opponents in Razgrad, the visitors now set out to avoid another European defeat on the road with three of their last four continental games on the road ending in a loss.
FK Zalgiris Europa League form:
FK Zalgiris form (all competitions):
Ludogorets Razgrad Europa League form:
Ludogorets Razgrad form (all competitions):
Team News
Zalgiris' Donatas Kazlauskas is suspended for this one after the 28-year-old received his marching orders in the first leg for two bookable offences.
Dominik Yankov and Rick are both available for Ludogorets once again having missed the aforementioned game through a one-match suspension.
The Brazilian Renan Oliveira continues to deliver the goods for the home side with three goals in his last as many games and he is definitely one worth keeping an eye on here.
Cauly Oliveira and Claude Goncalves remain sidelined through muscle and knee injuries respectively, ruling the duo of Thursday's contest in Vilnius.
FK Zalgiris possible starting lineup:
Duka; Bopesu, Kazukolovas, Kashken, Mamic; Tatomirovic, Jarusevicius, Kyeremeh, Kuklys; Tadic, Oliveira
Ludogorets Razgrad possible starting lineup:
Sluga; Cicinho, Verdon, Gropper, Nedyalkov; Yordanov, Piotrowski, Delev; Tekpetey, Igor, Despodov
We say: FK Zalgiris 1-1 Ludogorets Razgrad (Ludogorets Razgrad to win 2-1 on aggregate)
In what is set to be an all-or-nothing affair, we expect an absorbing contest with both teams going at each other over the course of the 90 minutes. However, we are tipping a share of the spoils here with the away side going through on aggregate.