|Lennon has busy season ahead of him chasing rivals Glasgow Rangers and competing in Europa League [GALLO/GETTY]
Swiss club Sion, kicked out of the Europa League for fielding ineligible players in a playoff tie, lost their appeal against UEFA's decision on Tuesday.
"The UEFA appeals committee rejected FC Sion's appeal against their expulsion from the group stages of this season's Europa League," said Celtic, the club who took their place in Group I.
"Celtic will (now) take on Atletico Madrid, Udinese and Stade Rennes," the Scottish club added on their website.
Atletico will host Neil Lennon's Celtic on Thursday.
Earlier in the day Sion, who beat Celtic 3-1 on aggregate in a playoff tie last month, said they had won a Swiss court order re-admitting them to the tournament.
However, the statutes of UEFA and world soccer's governing body FIFA ban clubs and national federations from taking football matters to civil courts.
"The court ordered UEFA to admit Sion as a participant in the Europa League and to take every measure to integrate them into Group I," Sion said on their website.
Sion added the court ordered that six players they signed this summer must be considered by UEFA as eligible, despite FIFA saying the club were subject to a transfer ban at the time.
"The regional tribunal in the canton of Vaud also ordered UEFA to consider Stefan Glarner, Billy Ketkeophomphone, Mario Mutsch, Pascal Feindouno, Jose Goncalves and Gabri to be recognised as Sion players and to admit them to the Europa League," said the Swiss club.
"This order is to be executed immediately."
European football's ruling body UEFA said it would make a statement later.
"UEFA also received today a court decision from the Tribunal Cantonal de Vaud and will issue a statement in this respect at a later stage," it said.
The FIFA ban was imposed after Sion were found guilty of inducing an Egyptian player to join them while he was still under contract to another club.
Swiss Cup winners Sion were initially banned from fielding the players in the Swiss League which then reversed the decision after the players took their case to a civil court.