Sporting Braga won a chaotic Europa League match at Parkhead with goals in either half, adding to Celtic’s European humiliation.
Kasper Schmeichel had an error-filled game in goal and failed to stop Ricardo Horta’s early long-range shot, which stunned the Celtic Park crowd to quiet.
The Dane then did well to keep out a late attempt, but was helpless when the ball bounced off Gabri Martinez’s poor clearing and into the net to seal the victory.
After failing to qualify for the Champions League against Kairat Almaty and drawing their first Europa League match against Red Star Belgrade, Celtic’s European campaign continued to be dismal.
In fact, the drop-off since last season has been so extreme that Brendan Rodgers’ team may struggle to qualify for the Europa League’s further stages unless they can regain their footing swiftly.
Braga dominated the first half of this encounter, prompting Rodgers to modify his formation after the interval in the expectation that a back three and additional players in the middle would help to consolidate his team.
The Scottish champions improved after that and believed they had leveled when Kelechi Iheanacho simply tapped home following an error by the Braga defense.
His jubilation was cut short as referee Tobias Stieler blew for handball, a decision supported by a long video assistant referee (VAR) review.
Braga then had goalkeeper Lukas Hornicek to thank for two outstanding saves as Celtic piled on the pressure in pursuit of an equalizer.
First, he leapt to his left to save a Kieran Tierney header, then hurled himself to the opposite corner to tip over Sebastian Tounekti’s curling effort that appeared to be heading for the net.
Following the formation change, Rodgers brought on a number of replacements, including Reo Hatate, Arne Engels, and James Forrest, but none of them had the quality to score the goal Celtic required.
Celtic proved they are not good enough for the Champions League by failing to score in 210 minutes against Kazakh club Kairat.
The seventh-placed team in Portugal’s first division has now thoroughly examined their credentials for the Europa League.
Braga is a decent team that has already beaten Celtic and Feyenoord in this league season.
They are far from a quality European team, however, and this setback will sting Celtic if they have any hopes of reaching the competition’s knockout round.
One point from the first half-dozen available will not suffice, and Rodgers’ players exhibited a level of disarray and vulnerability that the manager will dislike.
For much of the first half, his team was completely outplayed, so he switched to a back three with wing-backs instead of his usual 4-3-3 system.
It was unable to generate a goal, and Celtic’s lack of bite will concern the manager. They were unable to stop scoring last season. This term has been very difficult for them.
Celtic return to domestic action on Sunday, when Jens Berthel Askou’s new-look Motherwell travel to Glasgow for Scottish Premiership duty (15:00 BST).