(CNN) -- Do you believe in second chances? It would appear that those wearing the green and white of Celtic do.
Having been handed a brutal beating by Polish side Legia Warsaw in the third qualifying round of the Champions League, Celtic's European adventure appeared to be over before it had started.
A 4-1 defeat in the Polish capital was followed by a 2-0 home defeat -- a result which should have sent Legia through to the playoff stage.
Except it didn't. Instead, UEFA, the game's European governing body, was called in to rule over claims Legia had fielded an ineligible player during the tie.
Bartosz Bereszynski, who entered the action with two minutes of the second leg remaining, was supposed to be serving a ban.
It was his presence on the field which meant UEFA awarded the game to Celtic 3-0, making it 4-4 on aggregate and allowing the Scottish champion to progress on away goals.
While Legia protested, even taking their failed case to CAS, the Court for the Arbitration of Sport, Celtic ensured it made the most of it fortune.
A game against Slovenian champion Maribor was Celtic's reward with the opportunity to play some of European football's biggest names the prize.
Celtic, which won the European Cup in 1967, took the lead within six minutes of the kickoff when Callum McGregor fired home from close range after Jo Inge Berget's effort was diverted into his path.
Maribor, which last reached the group stage of the tournament in 1999, overcame Maccabi Tel Aviv 3-2 on aggregate in the previous round.
And it soon carved Celtic open to claim a deserved equalizer when Damjar Bohar ran through to slot the ball past the onrushing Craig Gordon.
Both teams had opportunities to win the game with Charlie Mulgrew and Virgil van Dijk going close for the visitors, while Tavares' rasping effort flew just over the crossbar for Maribor.
The two will meet again next Tuesday with Celtic now the firm favorite to progress following the 1-1 draw.
Elsewhere, Porto, the 2004 champion, gained an impressive 1-0 win at French side Lille.
Hector Herrera's 61st minute strike was enough to give Porto a slender advantage going into next week's second leg.
In Belgium, Oleg Shatov scored the only goal of the game as Zenit St Petersburg recorded a 1-0 away win at Standard Liege.
In the night's other games, Slovan Bratislava drew 1-1 with BATE Borisov, while Aalborg and Apoel finished 1-1.