The hosts got past Hacken in the playoff round to reach this stage, while their visitors navigated their way through three qualifying rounds to reach the main competition for the second straight season.
Match preview
Heidenheim will begin their Europa Conference League league-phase bid on Thursday, in what is their first-ever continental campaign after a historic eighth-placed finish in their debut Bundesliga season last time around.
That earned them a place in the playoff round of Europe's tertiary competition, leaving them needing one aggregate victory to book a spot in the league phase, and Frank Schmidt's side took a 2-1 advantage into their home leg against Hacken in late August as Sirlord Conteh and Leo Scienza got on the scoresheet in Sweden.
The slender lead did not appear to be enough for the German outfit, though, as they fell 2-1 behind in the second leg with 10 minutes remaining, but Paul Wanner drew them back level on the night with six minutes remaining before Mathias Honsak wrapped up a 5-3 aggregate win in injury time.
Schmidt's men now return to continental action on the back of a pleasing start to their second consecutive Bundesliga campaign, currently sat sixth in Germany's top flight on nine points from their first five outings, most recently bouncing back from consecutive defeats with a 2-0 victory away at Mainz on Thursday thanks to goals from Marvin Pieringer and Jan Schoppner in the 15th and 86th minutes respectively.
With confidence back on their side, Heidenheim will now bid to make the most of home advantage on Thursday and put their first three points on the board at the first time of asking in the league phase.
In their way stand an Olimpija Ljubljana side who have fought through three stages of qualifying to reach the main Europa Conference League competition for the second straight season.
Following a third-placed finish in the Slovenian PrvaLiga last time around, Thursday's visitors entered qualifying for Europe's tertiary competition in the second round, and they cruised past Polissya Zhytomyr and Sheriff Tiraspol to book a place in the playoff round.
HNK Rijeka then stood in their way, and the Dragons progressed to the league phase in dominant fashion, drawing 1-1 in Croatia and dishing out a 5-0 beating on home turf thanks to goals from Raul Florucz, Dino Kojic and Pedro Lucas alongside a Thalisson brace.
Still unbeaten on all fronts after 17 games of the season, Victor Sanchez's side boast a near-perfect record since that latest continental triumph, progressing to the third round of the Slovenian Cup with a 3-0 win over Domzale and adding 10 points to their PrvaLiga tally in four more attempts, most recently beating Primorje 2-0 away from home with Florucz again on the scoresheet alongside Ivan Durdov.
Now sat top of the domestic top flight after 10 outings in their bid to regain the title this term, NK Olimpija Ljubljana will turn their focus back to their continental pursuits on Thursday and bid to open their account for the league phase in Germany.
Heidenheim Europa Conference League form:
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Heidenheim form (all competitions):
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NK Olimpija Ljubljana Europa Conference League form:
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NK Olimpija Ljubljana form (all competitions):
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Team News
Heidenheim should field a similar starting XI on Thursday to the weekend's victory over Mainz, with Mathias Honsak, Thomas Keller and Leo Scienza set to remain sidelined by injuries, while midfielder Niklas Dorsch is available despite being sent off in the final 10 minutes of that triumph.
He should again join Jan Schoppner in the engine room, while 18-year-old Paul Wanner will continue to operate further forward having already contributed four goals and two assists in just seven appearances since arriving on loan from Bayern Munich.
Top scorer Maximilian Breunig will compete to come back into the attack from the start, having notched up five goals of his own this term, although Marvin Pieringer should keep him place after putting them ahead on Saturday.
Olimpija Ljubljana could also field a similar starting XI to their domestic triumph last time out, with Ivan Durdov bound to again lead the line after netting his fourth goal of the season in that game.
He will continue to join Pedro Lucas, who has netted five goals of his own this term, while Raul Florucz leads the squad with six in his 11 appearances thus far and should return on the wing from the outset after scoring off the bench at the weekend.
Elsewhere, Peter Agba and Agustin Doffo are key men in midfield and should continue their partnership, while Ahmet Muhamedbegovic and Marcel Ratnik will again feature at the heart of the back four on the back of another clean sheet.
Heidenheim possible starting lineup:
Muller; Busch, Mainka, Gimber, Fohrenbachl; Schoppner, Dorsch; Kaufmann, Wanner, Breunig; Pieringer
NK Olimpija Ljubljana possible starting lineup:
Vidovsek; Silva, Ratnik, Muhamedbegovic, Sualehe; Florucz, Doffo, Agba, Blanco; Lucas, Durdov