Scottish champions Celtic will look to use their reprieve from Champions League oblivion and gain a positive result away at Slovenian titleholders Maribor on Wednesday in the first leg of their play-off.

Celtic were soundly beaten by Polish outfit Legia Warsaw in the third qualifying round only to regain their place in the competition thanks to an administrative error by their opponents.

Legia went to the Court of Arbitration for Sport (CAS) in a bid to overturn UEFA's original decision to punish them for sending on substitute Bartosz Bereszynski at the end of the second leg -- with Legia leading 6-1 on aggregate -- when he was deemed as being ineligible to play as he should still have been serving a suspension.

However, the CAS refused to make a quick ruling on the matter, leaving Celtic to focus their minds on the challenge of Maribor as they chase a place in the lucrative group stage.

Celtic manager Ronny Deila at least can take his side -- winners of the European Cup back in 1967 -- to Slovenia in better heart than when they faced Legia as since then the champions have begun their domestic title defence with two wins, the second one a 6-1 humbling of Dundee United.

"It looks like the players now understand what they've got to do so it was a good feeling for me," said the 38-year-old Norwegian following Saturday's victory.

"We created a lot of things and kept the ball well and also our set-plays were better."

Despite the comprehensive nature of their win, Deila says there is still room for improvement.

"We win together and we lose together but we still need to work on our performances," the Celtic boss added.

"We showed today that we have a very good team and there is a lot of good quality."

Another former winner of the competition, the 2004 champions Porto, are also in action away in the first leg at French side Lille, who enjoy a proud record when it comes to the play-offs having never lost in three previous appearances.

Porto do not represent as formidable a challenge as they did when they won the trophy nor indeed when under Andres Villa-Boas they won the Europa League in 2011 with an attack containing Colombian Radamel Falcao and Brazilian frontman Hulk.

Indeed Porto come to France having offloaded two key players, French central defender Eliaquim Mangala and experienced Belgian international midfielder Steven Defour, who left for Manchester City and Anderlecht respectively in recent weeks.

Lille have begun their Ligue 1 campaign with a win and a draw but scored just the one goal through Belgian teenager Divock Origi, whose performances at the World Cup earned him a move to Liverpool before he returned to the French side on loan.

Lille's Danish international central defender Simon Kjaer, who along with his fellow defenders has not conceded a goal in the two Ligue 1 games, said that they were in a good condition to beat the Portuguese giants.

"Of course we will be ready for Porto, we have to be," said the 25-year-old.

"We have been excellent in terms of playing as a team even if offensively we could have been sharper.

"We are confident for the next match, the team can only improve."

Villas-Boas and Hulk have been reunited at Zenit St Petersburg and both have not enjoyed the smoothest of rides since their halcyon days at Porto.

However, the Russian side has made a sparkling start to their league campaign winning all four of their games and should have enough firepower for Belgian side Standard Liege.

Fixtures (kick-offs all 1845GMT)

Standard Liege (BEL) v Zenit St Petersburg (RUS)

Lille (FRA) v FC Porto (POR)

Maribor (SLO) v Celtic (SCO)

Aalborg (DEN) v Apoel FC (CYP)

Slovan Bratislava (SVK) v BATE Borisov (BLR)