Both sides head into the meeting unbeaten after two matches, although the visitors are winless having drawn twice.
Match preview
Union Berlin, of course, were pipped to the fourth Champions League qualification spot by Leipzig by a single point last season, so may feel that they owe their forthcoming opponents a slice of revenge on Saturday.
Urs Fischer's side have delivered two successive top-half finishes since being promoted to Germany's top-flight for the first time in their history in 2020, and with one win and one draw from their opening two matches, they do not look like stopping there.
In truth, though, their 0-0 draw against Mainz 05 last weekend was a match to be missed. Extremely hot conditions did not help either side play at their best, in fairness, with both managers keen to avoid being caught in transition.
Theoson Siebatcheu, who made himself an instant hero with a debut Bundesliga goal against city rivals Hertha Berlin on matchday one, will hope that more service is forthcoming in behind Leipzig's higher defensive line.
It has not been an ideal start to the campaign for Leipzig, who may have believed that they could sustain a title challenge this season having splashed £50m on Timo Werner, David Raum and Xaver Schlager this summer.
Werner was thrown straight in for his second debut against FC Koln last weekend, with the former Chelsea striker getting his Leipzig career back up and running in perfect fashion when his speculative effort from 25 yards somehow went through the body of Marvin Schwabe and into the back of the net.
However, after Christopher Nkunku - who was awarded his Bundesliga Player of the Year trophy prior to kickoff - missed an excellent chance to double his side's lead, Koln went straight up the other end and equalised after Florian Kainz's accurate low cross found Florian Dietz at the back post.
Kainz was in the thick of the action throughout, with the midfielder's physical presence provoking Dominik Szoboszlai into a nasty elbow which earned the Hungary midfielder a straight red card moments before half time.
However, Nkunku redeemed his earlier miss with a superbly searing run and finish into the far corner, but with a man advantage Koln inevitably rallied for a second equaliser. Kainz's dangerous corner was clumsily bundled over his own goal-line by Josko Gvardiol, with both sides understandably settling for a point thereafter.
While Domenico Tedesco will not be pushing the panic button just yet given the mitigating circumstances surrounding both of his side's draws so far, Saturday's tough trip to Union Berlin has not come at the best moment for his side, with pressure increasing on them to gain their first league win of the season.
Union Berlin Bundesliga form:
Union Berlin form (all competitions):
RB Leipzig Bundesliga form:
RB Leipzig form (all competitions):
Team News
Union Berlin will be without Timo Baumgartl (match fitness) and Fabio Schneider (knee) on Saturday.
Despite playing out a dour draw in Mainz last time out, Fischer is unlikely to make any changes to his starting XI, with Siebatcheu and Sheraldo Becker set to combine with their pace and power in transition.
Leipzig, meanwhile, will travel without Lukas Klostermann (ankle) and Youssouf Poulsen (thigh), while Szoboszlai will serve a two-match suspension after his dismissal last weekend.
Kevin Kampl will likely come into the side to occupy a deep-lying midfield role alongside Benjamin Henrichs, who has impressed in a more central role so far this season, while Gvardiol should start in place of Marcel Halstenberg in defence despite the Croatian's unfortunate own goal against Koln.
Union Berlin possible starting lineup:
Ronnow; Jaeckel, Knoche, Leite; Trimmel, Khedira, Haberer, Grießelmann; Haraguchi; Becker, Siebatcheu
RB Leipzig possible starting lineup:
Gulasci; Simakan, Orban, Gvardiol; Novoa, Kampl, Henrichs, Raum; Olmo; Nkunku, Werner
We say: Union Berlin 1-1 RB Leipzig
It is hard to split these two teams, with Leipzig obviously possessing superior individual quality, but Union Berlin's counter-attacking style is likely to hurt them.
As such, it would be no surprise to see Leipzig draw a third successive match, with both teams probably content enough with that potential outcome.