The home side made a positive start to the contest, and they ought to have taken the lead with nine minutes on the clock when a pinpoint cross into the area from the left found Svit Seslar unmarked in the area. However, the midfielder sent his close-range header over the crossbar.
Despite Celje’s bright start, they found themselves behind moments later. A long pass upfield by Kenan Bajric was expertly controlled by Andraz Sporar before the forward lifted the ball over the onrushing Zan-Luk Leban to give the visitors the lead against the run of play.
To Celje’s credit, the Slovenian side weren’t affected by going behind and continued to pose a threat going forward. Pijus Sirvys’ first-time effort from the edge of the area was gathered by Dominik Takac before Andrej Kotnik saw his header brilliantly saved by the right hand of the Slovan stopper.
The hosts deserved to be all square at the break, and they were given a golden opportunity to do so six minutes before half time.
After consulting the pitchside monitor, the referee adjudged that Tigran Barseghyan had brought Yaya Dukuly down inside the area, and Svit Seslar made no mistake from the spot to draw Celje level on the night and in the tie.
The home side were buoyed by their unbeaten record at Stadion N’dezele so far this season, but they were finding it more challenging to create opportunities than they did in the first half.
It took over 20 minutes for the hosts to threaten the Sky Blues’ goal after the restart, and they very nearly took the lead as Dukuly showed great skill to open up space to shoot from 25 yards, with the winger’s effort beating Takac but hitting the right post and ricocheting away to safety.
Having posed little threat, the away side came agonisingly close to snatching victory when Roman Cerepkai’s header - which looked destined for the top left-hand corner - was pushed behind by Leban.
Armandas Kucys then spurned a glorious chance in second-half stoppage time when he miscued his effort from a cross with the goal at his mercy after Takac had failed to gather.
Slovan were winless in their last 13 UEFA away games, but dealt the decisive blow in the 100th minute after battling hard to stay in the contest.
After regaining possession in midfield, they broke forward with Nino Marcelli finding Cristian Martinez, who lifted the ball over Leban and into the far corner to send the away supporters wild.
The Slovaks have now won three consecutive away matches in Europe for the first time in their history, and they can now look forward to returning to the UCL after a one-season absence.
Flashscore Man of the Match: Kenan Bajric (Slovan Bratislava)