Celtic got a taste of their own medicine in Germany as they came crashing back down to earth with a 7-1 Champions League defeat against Borussia Dortmund.
Brendan Rodgers’ side had won their previous 17 matches and scored 33 goals this season before arriving at Signal Iduna Park in confident mood, fresh from a 6-0 win over St Johnstone on Saturday and a 5-1 victory over Slovan Bratislava in their Champions League opener.
But they found the step up in class too much to handle as they were overrun by last year’s runners-up, not helped by the absence of centre-back Cameron Carter-Vickers and some slack passing throughout their team.
Celtic were briefly level when Daizen Maeda cancelled out Emre Can’s early penalty but Karim Adeyemi bagged a first-half hat-trick and Serhou Guirassy also scored from the spot before the interval.
Guirassy and Felix Nmecha piled on the misery in the second half as Rodgers found himself presiding over another Champions League thrashing.
Celtic’s heaviest European defeat remains a 7-0 loss in Barcelona during Rodgers’ first spell in charge and he also suffered a 7-1 defeat against Paris St Germain and a 6-0 loss to Atletico Madrid.
The warning signs were evident from early on when Adeyemi had numerous options but could not find a pass or shot, and Can provided the opener in the seventh minute after Kasper Schmeichel brought down Jamie Gittens after the England Under-21 winger had burst beyond Celtic’s back four.
Celtic were level inside two minutes when Maeda bundled home Arne Engels’ cross but Dortmund regained the lead in the same timescale. Guirassy’s flick to the unmarked Julian Brandt left the Celtic back line vulnerable and Adeyemi ran on to the through ball and fired the ball high into the net off the foot of Auston Trusty.
Schmeichel made two decent stops to keep Celtic in it and the Hoops had a let-off when Pascal Gross opted to pass instead of shooting.
Maeda looked a threat at the other end and fired wide from 25 yards but he was beaten to the tackle by Adeyemi following a 29th-minute corner before the forward fizzed the ball inside Schmeichel’s near post and into the roof of the net from a difficult angle.
Celtic continued to give the ball away and the chances kept coming. Adeyemi came close from 25 yards after Paulo Bernardo’s loose pass and Schmeichel saved from Gross before another wave of goals.
Engels caught Adeyemi on the foot as the pair contested a bouncing ball and Guirassy did the damage from the 40th-minute penalty. Celtic shot themselves in the foot again two minutes later when Maeda overran the ball on the edge of his box and Adeyemi supplied another lethal finish.
Rodgers made a double substitution at the interval, putting Reo Hatate on for Bernardo and Alex Valle for Greg Taylor, who had been struggling with a calf issue.
Celtic were spared more punishment from Adeyemi when the 22-year-old Germany international was forced off by an injury just after the restart.
But the pattern of the game did not change and Schmeichel made saves from 18-year-old substitute Julien Duranville and Julian Ryerson.
A poor cross from Nicolas Kuhn and a wayward shot from Hatate prevented Celtic from reducing the arrears before Guirassy turned Liam Scales one way and another before stabbing home the sixth in the 66th minute.
The Celtic fans kept singing and their team kept trying to reward them. Hatate came closer from 22 yards and fellow sub Adam Idah could only head Valle’s cross into the arms of Gregor Kobel from close range.
The pain was not finished, though, and Nmecha drilled home the seventh in the 79th minute after the ball broke for the substitute in the box.
Schmeichel denied Duranville from a one-on-one to prevent a record European defeat and Celtic now need to regroup before taking on Atalanta in Italy in their next game in the tournament.