The winners of this two-legged contest will take on either Lithuanian side FK Zalgiris or Turkish giants Galatasaray in the third qualifying round next month.
Match preview
Ludogorets appeared to be heading for an early exit from Champions League qualifying when they suffered a 2-0 first-leg away defeat to Kosovan outfit KF Ballkani in the first round earlier this month.
However, Ivaylo Petev's side turned the tie on its head in dramatic fashion when they secured a thumping 4-0 second-leg victory on home soil last week, with goals from Bernard Tekpetey (2), Matias Tissera and Caio Vidal helping them record a 4-2 aggregate triumph.
Ludogorets, who are seeking to reach the Champions League group stage for just the third time in their history, have come up short in each of the last six years of qualifying, suffering elimination in the second round on three occasions, the third round twice and the playoff round once.
Last season's Bulgarian First League champions began the defence of their title with a disappointing loss to newly-promoted Krumovgrad just under two weeks ago, but they have since bounce back with their four-goal Champions League win over Ballkani and a thumping 5-0 top-flight victory at home against Etar VT last weekend, with Petev's side now brimming with confidence ahead of Wednesday's contest.
The same cannot be said of Olimpija Ljubljana, though, as they head to Bulgaria after suffering a 2-1 away defeat against Koper in the opening game of the new Slovenian PrvaLiga season last weekend.
Olimpia had previously won seven of their last eight matches in all competitions, with five friendly victories out of six followed by successive 2-1 wins home and away against Valmiera in the Champions League first qualifying round.
However, the three-time top-flight champions and current holders were unable to come out on top against Koper, and they were two goals down before Svit Seslar netted what proved to be only a consolation strike in second-half stoppage time.
Last weekend's loss was the first for manager Joao Henriques since taking the reigns in June, and the Portuguese boss is keen to see a response from his side on Wednesday as they endeavour to boost their hopes of reaching the Champions League group stage for the first time in their history.
Ludogorets Razgrad Champions League form:
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Ludogorets Razgrad form (all competitions):
NK Olimpija Ljubljana Champions League form:
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NK Olimpija Ljubljana form (all competitions):
Team News
Ludogorets are set to be without Dinis Almeida and Denny Gropper as they continue to recover from ligament injuries, while Anton Nedyalkov has been sidelined since March after undergoing heel surgery.
However, Rick made his first appearance in eight months last weekend after recovering from a ligament tear, and the Brazilian winger will be available for selection again on Wednesday.
Summer signing Kwadwo Duah, who has joined from Nuremburg, made his competitive debut last time out, but the striker will face competition from Matias Tissera, who scored 16 goals in 47 games last season, for a start up front against Olimpija.
As for the visitors, Henriques will consider recalling a number of first-team regulars including Seslar, Mustafa Nukic, David Sualehe and Ahmet Muhamedbegovic, with the latter two pushing for starts in defence.
Eighteen-year-old Marcel Ratnik could partner Muhamedbegovic at the hearts of the defence, while Mario Kvesic, who scored a team-high 13 goals last term, could start on the left flank ahead of Rui Pedro.
Ludogorets Razgrad possible starting lineup:
Padt; Witry, Plastun, Russo, Heister; Yankov, Piotrowiski, Goncalves; Despodov, Tissera, Tekpetey
NK Olimpija Ljubljana possible starting lineup:
Vidovsek; Silva, Ratnik, Muhamedbegovic, Sualehe; Seslar, Doffo, Elsnik, Kvesic; Posavec; Nukic