The Reds currently sit top of Group E after beating LASK Linz 3-1 in gameweek one, while their Belgian counterparts played out a 1-1 draw with Toulouse in their opening group fixture.
Match preview
Liverpool's 17-game unbeaten run in the Premier League was brought to an end in both dramatic and controversial circumstances when they suffered a 2-1 defeat at Tottenham Hotspur on Saturday - their first defeat in any competition since April 1.
Luis Diaz had a first-half goal wrongly disallowed due to a "significant human error" by VAR, just 10 minutes after Curtis Jones was contentiously dismissed for a late tackle following a VAR review. The Reds were then reduced to nine men midway through the second half when Diogo Jota quickly picked up two yellow cards, before salt was rubbed into Liverpool's wounds when Joel Matip turned a Pedro Porro cross into his own net in the 96th minute.
Jurgen Klopp vented his frustration at the officials after the match and Liverpool - who have slipped down to fourth in the top-flight table - have since released a strong statement claiming that "sporting integrity has been undermined", and they intend to "explore the range of options" in an attempt to resolve the matter.
Amidst the ongoing VAR controversy in the Premier League, Liverpool will look to turn their frowns upside down when they resume their Europa League group-stage campaign on Thursday with a first-ever meeting against Union SG, and they will certainly welcome a midweek return to Anfield.
Indeed, the Reds have won 15 of their last 21 Europa League home matches and have won each of their last seven group-stage games in UEFA competition, while they have also lost only one of their previous 15 meetings with Belgian teams - a 3-1 defeat to Anderlecht in the 1978 European Super Cup.
Competing in the Europa League group stage for the second successive season, Union SG managed to rescue a point on home soil in their opening Group E match with Toulouse two weeks ago.
Thijs Dallinga put the French visitors in front at the break, but Union SG restored parity in the 69th minute courtesy of in-form attacker Mohamed Amoura, who came off the substitutes' bench to net his fourth goal in three games.
Since then, Alexander Blessin's side have won three consecutive Belgian Pro League matches, including last weekend's 3-1 home success over Charleroi to help the Saint-Gilles-based club maintain their position at the top of the table, albeit on goal difference after six games.
Union SG reached the quarter-finals in their debut Europa League campaign in 2022-23 after topping their group, but finishing above Liverpool at the summit of Group E this term seems a tall order, so securing second place ahead of Toulouse and LASK Linz is a realistic target for Blessin and co.
Les Unionistes head into Thursday's contest seeking to become the first Belgian club to avoid defeat at Liverpool, and they can walk out at Anfield with optimism considering they did not lost any of their five away games in last season's Europa League.
Union SG's only previous meeting with English opposition came back in the 1958-60 Inter-Cities Fairs Cup when they lost both legs against Birmingham City.
Liverpool Europa League form:
W
Liverpool form (all competitions):
W
W
W
W
W
L
Union SG Europa League form:
W
W
D
Union SG form (all competitions):
D
L
D
W
W
W
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Team News
Liverpool forward Cody Gakpo is facing several weeks out with a knee injury sustained after scoring a first-half equaliser against Spurs last weekend, while Thiago Alcantara (hip) and Stefan Bajcetic (calf) both remain in the treatment room.
Klopp is expected to freshen up his starting lineup, with Caoimhin Kelleher set to replace Alisson Becker in goal, while Joe Gomez and Kostas Tsimikas could be handed starts at full-back, with Trent Alexander-Arnold beginning as a substitute having only recently recovered from a hamstring issue.
Darwin Nunez - who has been directly involved in eight goals (six goals and two assists) in as many Europa League games - is the most likely candidate to replace the injured Gakpo up front, while the likes of Jota, Ryan Gravenberch, Wataru Endo and Harvey Elliott will all be hoping to force their way into the first XI after beginning as substitutes last weekend.
As for Union SG, their only injury concern is with star striker Dennis Eckert Ayensa, who has missed the last four games with a knock and will be assessed ahead of Thursday's clash - the Spaniard has scores seven goals in eight appearances so far this season.
The potential absence of Ayensa is set to see Gustaf Nilsson lead the line, with Amoura, Cameron Puertas and Lazare Amani all looking to earn a starting spot in the final third.
Boca Juniors loanee Kevin Mac Allister - the brother of Liverpool midfielder Alexis Mac Allister - is expected to start in a back three with former Portsmouth defender Christian Burgess and Fedde Leysen, while Alessio Castro-Montes and Loic Lapoussin could be recalled to start on the flanks.
Liverpool possible starting lineup:
Kelleher; Gomez, Konate, Van Dijk, Tsimikas; Elliott, Endo, Gravenberch; Salah, Nunez, Jota
Union SG possible starting lineup:
Morris; Mac Allister, Burgess, Leysen; Castro-Montes, Sadiki, Vanhoutte, Lapoussin; Amani, Nilsson, Puertas
We say: Liverpool 3-1 Union SG
Union SG's impressive away form bodes well heading to Anfield, and they will fancy their chances of finding the net considering Liverpool have conceded in 10 of their last 11 games in all competitions.