Celtic have been reinstated to the Champions League after Legia Warsaw had their third qualifying round second-leg win over the Scottish champions overturned for fielding an ineligible player, UEFA has announced.
Polish side Legia won the tie 6-1 on aggregate, but were found to have fielded an ineligible player in the second leg by European football's governing body on Thursday night.
Bartosz Bereszynski, who was an 86th-minute substitute at Murrayfield, was sent off for violent conduct against Apollon in the final match of Legia's Europa League campaign last season.
The full-back missed both of Legia's matches against St Patrick's Athletic in the second qualifying round and sat out the 4-1 first-leg victory over Celtic.
UEFA's investigation centred on whether the player was registered in Legia's squad against the Irish side in order to allow a three-match suspension to take effect.
Champions League regulations state that players must be registered with UEFA within requested deadlines and that "only eligible players can serve pending suspensions."
UEFA's disciplinary regulations decree that a match may be declared a forfeit if an ineligible player participates, "as long as the opposing team files a protest."
The team forfeiting the match is deemed to have lost 3-0 -- an adjusted result which puts Celtic through to the playoff round on the away goals rule.
An official UEFA statement read: "The UEFA Control, Ethics and Disciplinary Body has met today and announced the following disciplinary decision following the 2014-15 UEFA Champions League third qualifying round tie in Edinburgh between Celtic FC and Legia Warsaw on August 6, 2014.
"Legia have been sanctioned for fielding an ineligible player [article 18 of the UEFA Champions League regulations and article 21 of the Disciplinary Regulations]. The match has been declared as forfeit meaning Legia Warsaw have lost the match 3-0.
"As a consequence, Celtic have qualified for the UEFA Champions League playoffs on away goals [agg: 4-4] and Legia will compete in the UEFA Europa League playoffs.
"In addition the player Bartosz Bereszynski has been suspended for one additional UEFA competition match for which he would be otherwise eligible. This suspension shall be added to the remaining two match suspension which the player still has to serve in accordance with the Control and Disciplinary Body decision of Feb. 13, 2014."
Legia Warsaw have five days within which to lodge an appeal, and a statement on the Polish's club website indicated they had requested UEFA's reasoning for the ruling before making a decision.
Legia chairman Boguslaw Lesnodorski has taken full responsibility for the mistake and took to Twitter to apologise to the club's fans.
"The Champions League not for us this year... I let you down," he wrote.
Nie dla Nas LM w tym roku... Zawiodłem- B(L)1916 (@BL_1916) August 8, 2014
The UEFA administration decides on eligibility questions while any appeals are dealt with by UEFA's control and disciplinary body.
Celtic also benefited from an ineligibility ruling in the 2011-12 campaign, when they were reinstated into the Europa League group stages despite a qualifying defeat to Sion.
The Swiss side were ruled to have fielded five ineligible players after breaching a FIFA transfer ban and failed to reverse the decision during a lengthy legal battle.
Information from the Press Association was used in this report