Franck Haise's men are, by some distance, the biggest underachievers in the competition so far, with progression to the knockouts now looking beyond them.
Match preview
With just two points to their name after five matches, Nice find themselves 35th in the Europa League table, with only a pointless Dynamo Kyiv below them at this stage.
A home hammering at the hands of Rangers on matchday five saw Haise's side slip below the likes of Ludogorets and RFS on goal difference, and another poor result here could see them go bottom.
Only Qarabag have conceded more goals than Nice's 12 so far in the league phase, so it comes as no surprise that they have spent the longest amount of time trailing in the Europa League so far (69%), conceding the first goal in all five matches.
Away form further provides very little for the visitors to get excited about, with just one win from their last seven on the road across all competitions, but they did at least recover from back-to-back 4-1 defeats at the weekend.
OGC beat struggling Le Havre 2-1 on home soil, but that was just their fourth win in 14 games since beating Saint-Etienne 8-0 in September, a result which at the time looked like kickstarting a very promising season.
Nice have only faced one previous Belgian opponent, and that was Zulte-Waregem in this competition seven years ago, winning home and away by a combined score of 8-2, so nothing short of that will be enough to drag them back into contention to finish in the top 24.
It does not help matters the fact that opponents Union SG are in a fine run of form, even if they were held to a goalless draw by 10-man Cercle Brugge over the weekend.
That still extended Union's unbeaten run to nine games, in what has been a season of two halves so far for Sebastian Pocognoli's men.
Union went 450 minutes without scoring a goal earlier in the campaign, and did not open their European account until the 77th minute of matchday four, when Kevin Mac Allister earned them a draw against Roma.
The Belgian side had taken just one point from their opening three games against winnable opponents in Fenerbahce, Bodo/Glimt and Midtjylland, but while spurning those opportunities to give themselves a good chance of reaching the knockouts, the 1-0 win over Twente on matchday five has certainly put them in contention.
Union are 24th heading into matchday six, and two wins will likely be required for them to stay there at the conclusion of the league phase, and a tricky finish awaits, with Braga and Rangers to come in January.
That win over Twente means Union could win back-to-back games in Europe for just the second time if they taste success this week, and they have good history with French clubs on the continent.
Despite their inexperience at this level, they held Toulouse to two draws in last season's Europa League, while back in the 1960s, they also knocked Marseille out of the Inter-Cities Fairs Cup.
Union SG Europa League form:
L
D
L
D
W
Union SG form (all competitions):
D
W
D
W
W
D
Nice Europa League form:
D
L
L
D
L
Nice form (all competitions):
D
D
W
L
L
W
Team News
Union will be without Henok Teklab after he broke his leg, meaning he will not be seen until 2025, but Guillaume Francois, Alessio Castro-Montes and Mamadou Traore are all in contention to return from recent minor setbacks.
Koki Machida served a domestic suspension in the 0-0 draw with Cercle Brugge, but will be available again here and should return to the home side's starting XI.
Nice will also have Moise Bombito and Sofiane Diop available to them after they sat out the defeat to Rangers with European bans, and their returns are hugely important given the very long injury list Haise is facing at present.
Mohamed Abdelmonem will hope to recover from illness with other capable defenders Dante and Youssouf Ndayishimiye missing, while Jonathan Clauss, Ali Abdi and Melvin Bard are all absent at full-back.
One of the recent casualties is Mohamed-Ali Cho, who suffered a hamstring injury at the start of the month, joining fellow attacker and long-term absentee Terem Moffi on the sidelines.
Morgan Sanson, Antoine Mendy (both ankle) and Victor Orakpo (hernia) round off the eye-watering injury list Haise has to deal with ahead of this trip across the border.
Union SG possible starting lineup:
Moris; Khalaili, Mac Allister, Burgess, Sykes, Machida; Fuseini, Sadiki, Vanhoutte, Boufal; David
Nice possible starting lineup:
Bulka; Louchet, Rosario, Bombito, Nandjou; Boudaoui, Ndombele; Bouanani, Guessand, Boga; Laborde
We say: Union SG 1-1 Nice
Nice's worrying European form is unlikely to change against a side currently unbeaten in nine games, and it could spell the end of their chances to progress.
Written by
Andrew Delaney