The two group-stage hopefuls each earned a slice of the spoils in a 1-1 draw last week, and the midweek victors will advance to meet either Galatasaray or Zalgiris in the third round.
Match preview
Now being forced to juggle domestic and continental commitments following the resumption of the Slovenian PrvaLiga, national champions Olimpija Ljubljana posted a 4-2 win over Latvian outfit Valmiera in round one before making their sojourn to Bulgaria last week.
Joao Henriques's men were in dreamland when Timi Max Elsnik broke the deadlock after just 14 minutes, but Ludogorets levelled on the stroke of half time through Dominik Yankov, and there were no more goals to be had in Razgrad.
The Champions League hangover appeared to take its toll on Olimpija earlier in July, as they commenced the defence of their Slovenian title with a 2-1 loss to Koper before righting those wrongs when Rogaska came to town on Saturday.
Indeed, Henriques oversaw a five-star and 5-0 success, although he had his substitutes to thank for 80% of his side's goals, as Saar Fadida scored a scintillating hat-trick off the bench alongside an effort from fellow substitute Rui Pedro.
The seven-time Slovenian champions have only ever been present in the Champions League proper on one occasion, although that ended in a swift 7-0 aggregate loss to AC Milan in the first round of the inaugural 1992-93 edition, but home advantage may very well play its part for the Dragons in their efforts to make more continental waves.
In eerily similar fashion, Ludogorets have also started their new Bulgarian top-flight campaign with an opening defeat and 5-0 win, teaching Etar VT a footballing lesson before playing out their recent stalemate with Olimpija.
However, Ivaylo Petev's side did not have to concern themselves with domestic matters this weekend as they gear up for their Slovenian stopover, and Ludogorets are no strangers to emphatic European successes after an initial setback.
The Eagles were bested 2-0 by Ballkani in the first leg of their Champions League first-round qualifying tie before rectifying those errors with a 4-0 thrashing in the return fixture, and the 12-time Bulgarian champions have been present in a continental group stage in each of the last seven seasons.
Two-time Champions League group-stage participants in the 2014-15 and 2016-17 seasons, Ludogorets have since been demoted to Europa League and Europa Conference League level more often than not, but they could only reach the knockout round playoffs in the latter competition last term.
Nevertheless, the visitors have only suffered four second-round exits in Champions League qualifying, although two of those eliminations came after they had drawn the first leg, which certainly makes for pleasant reading for the Olimpija faithful.
NK Olimpija Ljubljana Champions League form:
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W
D
NK Olimpija Ljubljana form (all competitions):
Ludogorets Razgrad Champions League form:
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W
D
Ludogorets Razgrad form (all competitions):
Team News
Olimpija's five-goal thrashing of Rogaska may have appeared to be the perfect afternoon at first glance, but attacker Raul Florucz had to be withdrawn with just 17 minutes on the clock and may now be forced to sit out the second leg.
However, his replacement Fadida proved a capable deputy with a terrific treble, and the Israeli attacker will surely be a straight swap for Florucz out wide, while Pedro is also in line to return to the final third.
Defenders Ahmet Muhamedbegovic and David Sualehe could also return to the first XI after enjoying well-earned rests at the weekend, but Agustin Doffo is walking a tightrope, having already been booked twice in this year's Champions League.
Likewise, Ludogorets also have a fresh attacking injury concern bedevilling them, as Kwadwo Duah - who only joined from Nurnberg this summer - was only on the field for seven minutes in the first leg before picking up an ankle issue.
Local reports have claimed that Duah will not be fit to spearhead the charge this week, so Matias Tissera should be given the nod as Petev's central striker, no doubt with support from long-serving winger Kiril Despodov.
With captain Anton Nedyalkov recovering from an operation, Despodov ought to wear the armband for Ludogorets, while another left-back in Denny Gropper is nursing a cruciate ligament injury, guaranteeing a start for Marcel Heister.
NK Olimpija Ljubljana possible starting lineup:
Vidovsek; Silva, Ratnik, Karamatic, Sualehe; Doffo, Elsnik, Seslar; Fadida, Pedro, Motika
Ludogorets Razgrad possible starting lineup:
Padt; Witry, Russo, Plastun, Heister; Goncalves, Piotrowski; Despodov, Yankov, Tekpetey; Tissera
We say: NK Olimpija Ljubljana 2-1 Ludogorets Razgrad (Olimpija win 3-2 on aggregate)
Nothing could separate these two outfits last week, and a similarly tight affair should be in store in Ljubljana, where Ludogorets should no doubt benefit from their weekend break.