Kolo Toure made two poor defensive mistakes as Borussia Monchengladbach cruised to an away victory over Celtic.
Borussia Monchengladbach revived its hopes of progression from UEFA Champions League Group C with a deserved 2-0 win over Celtic in Glasgow on a night to forget for defender Kolo Toure.
Gladbach was the stronger team in a goalless first half and took the lead shortly before the hour mark when captain Lars Stindl struck after a defensive error from Toure.
Celtic did not have the same cutting edge as the visitors and failed to create a clear opportunity for an equaliser in the closing stages before another dreadful Toure mistake saw him lose possession, allowing Andre Hahn to seal the victory.
With Barcelona cruising to victory over Manchester City in the group's other game, Gladbach's win — its first in the European Cup since 1977 — puts it up to third place, just one point behind Pep Guardiola's side at the halfway stage.
After defeat in the first competitive meeting between the two teams, Celtic is bottom of the pile a further two points back and now in desperate need of a result in the return game in Germany on 2 November (AEDT).
Gladbach was the first to threaten, with Ibrahima Traore's strike after a cut-back from Oscar Wendt brilliantly saved by Craig Gordon, who then reacted quickly to prevent Hahn from converting the rebound.
Gordon had to make another strong stop when Julian Korb slipped a through a pass that allowed Jonas Hofmann to strike powerfully at goal.
Celtic was struggling to assert itself on the match, but wasted a good opportunity just before the break when Tom Rogic's precise throughball led to Scott Sinclair lashing a rushed finish over the bar.
The visitors got a deserved breakthrough on 57 minutes and it was Stindl's pass that started the attack.
When Toure failed in his attempt to shepherd the ball out of play, Hahn took advantage to find the onrushing Stindl and the skipper struck low between the legs of Gordon
Brendan Rodgers brought on Leigh Griffiths and Patrick Roberts in the closing stages, but despite the on-loan Manchester City winger's lively cameo, the hosts barely troubled Yann Sommer and it was game over with 13 minutes remaining.
Toure dawdled in possession, Stindl prodded a pass forward to Hahn and the striker lashed home a shot high past Gordon just as the former Liverpool defender attempted to challenge on a miserable evening for the hosts.