Paris: Miroslav Radovic scored twice to spark Polish champions Legia Warsaw into a 4-1 first-leg advantage over 10-man Celtic on Wednesday in the Champions League third qualifying round.
Callum McGregor had gifted Celtic an ideal start when he put the Scottish Premiership title-holders ahead on eight minutes, but the visitors` lead was cancelled out almost immediately by Radovic.
The Serbian striker then netted his second of the evening on 36 minutes to put Legia ahead before things took a further turn for the worse for Celtic as Nigerian centre-half Efe Ambrose was dismissed for a professional foul just prior to half-time.
Two late goals from Michal Zyro and Jakub Kosecki ultimately consigned Celtic to a heavy defeat that could have been even worse had Legia captain Ivica Vrdoljak not missed a pair of second-half penalties.
Hoops boss Ronny Deila gave a debut to Norwegian forward Jo Inge Berget, who joined on loan from Cardiff on Monday, with Anthony Stokes named to the bench after shaking off a hamstring problem.
The evening started in fine fashion for the visitors as McGregor, who scored on his competitive debut a fortnight ago in Reykjavik, continued his fine start to his Celtic career when he drifted in from the right and hammered a 20-yard strike beyond Legia goalkeeper Dusan Kuciak after eight minutes.
Legia were back on level terms just moments later, though, as Radovic was put through by Michal Zyro with the Serbian`s shot finding a way past Fraser Forster.
Kris Commons netted a league-best 27 goals in the Scottish top flight last season and the midfielder nearly restored Celtic`s advantage as he sliced through the Legia defence before firing narrowly over.
But Legia then went ahead nine minutes before the interval as Michal Kucharczyk cushioned a header back across goal for Radovic to stab home from close range.
Home `keeper Kuciak dived low to his right to keep out a McGregor effort and preserve the hosts` lead with Celtic suffering another damaging blow a minute before the break with Ambrose shown a straight red after taking out Kucharczyk just outside the area.
Legia sought to exploit their one-man advantage after half-time with Forster forced to produce a superb block to deny Zyro just after the restart.
The hosts were then awarded a penalty after Charlie Mulgrew brought down Ondrej Duda but Celtic were handed a reprieve as the subsequent spot-kick was put wide by Vrdoljak.
Undeterred Legia continued to threaten and were duly rewarded on 84 minutes as Radovic fashioned himself space down the right before delivering a cross which was headed home by Zyro.
A disastrous night for the Scots in Warsaw then saw Mulgrew concede a second penalty after a tug on Jakub Kosecki.
Remarkably Vrdoljak again failed to convert from the spot with Forster guessing correctly and diving to his left to push away the effort.
But Celtic were punished for more slack defending a minute into injury time as Kosecki steered home a fourth to complete a stunning victory for the Polish champions and leave Celtic`s Champions League dreams hanging by a thread.
Earlier, Sebastien Corchia marked his Lille debut in style with a goal and an assist to earn the French side a 2-0 win in Zurich against Grasshoppers of Switzerland.
Zenit Saint Petersburg had Belgium international Axel Witsel sent off as the Russians slumped to a 1-0 defeat against AEL Limassol in Cyprus.
Turkish side Besiktas beat 1970 European champions Feyenoord 2-1 in the Netherlands, while Panathinaikos, runners-up in 1971, played out a goalless draw away to Belgium`s Standard Liege.
The return legs are scheduled to be played over August 5-6 with the winners of each tie advancing to the play-off round.