celtic endured a frustrating return to european action as they struggled against swiss side sion in the first leg of their europa league qualifier.
an ineffectual strike partnership of anthony stokes and georgious samaras saw several chances to break the deadlock escape the glasgow outfit.
sion ignored warnings from fifa not to field players they consider ineligible.
jose goncalves, pascal feindouno, mario mutsch and gabri all took part against the governing body's wishes.
against that backdrop of controversy, celtic started brightly, with most of the action in the sion half for the opening 10 minutes.
georgios samaras samaras vexed the home crowd before being replaced by paddy mccourt the pairing of samaras and stokes up front failed to gel, though, with the greek in particular looking rusty, having not played so far this season.
sion, meanwhile, set out an ambitious formation, with guilherme alfonso and feindouno up front, and were happy to scrap for chances where they could find them.
michael dingsdag had the best of those, but could not convert from his free kick 35 yards out, samaras proving more useful in his own box as he cleared the shot away.
a rare positive for celtic was the performance of cha du-ri, the south korean charging up and down the right-hand side and delivering pinpoint crosses to the strikers.
however, the first half saw just six attempts on target by both sides and those frustrations continued after the restart.
samaras squandered another chance in the 50th minute, when cha delivered another perfect ball in from the right, only for the greek to head over the bar.
clearly not intimidated by warnings from fifa and uefa, sion coach laurent roussey introduced midfielder mutsch as a replacement for striker afonso.
neil lennon also made changes, replacing the industrious kris commons with james forrest and later brought on shaun maloney for anthony stokes.
jump media playermedia player helpout of media player. press enter to return or tab to continue. that decision was unpopular with the home crowd, who seemed intent on the withdrawal of samaras.
however, lennon was almost proved right seconds later when maloney earned a free kick after a challenge from adailton and delivered a near-perfect ball from the set-piece dipping over the sion wall, vanins performing heroics to stretch and parry the ball.
samaras made contact with the rebound but could not find the net.
the home support's nerves were further frayed in the 73rd minute when sion put the ball in the net.
feindouno silencing the celtic support as he put the ball past fraser forster and into the net but was judged to be offside in what appeared to be a close call for the croatian referee.
sion grew in confidence as the parkhead crowd grew more impatient, but celtic continued to create chances.
charlie mulgrew provided a superb ball for scott brown at the back post with 10 minutes remaining, the celtic captain's miss typical of a frustrating evening.
paddy mccourt's introduction at the expense of samaras gave the celtic fans a reason to cheer but had no impact on the scoreline.
the introduction of gabri by sion took the total of ineligible players to four, suggesting that this tie may yet be decided in the courts, rather than on the pitch.
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