Brendan Rodgers lamented "a game where every mistake we made got punished" after Celtic's 7-1 hammering at the hands of Borussia Dortmund. (More Football News)
Last year's Champions League runners-up Dortmund extended their club record unbeaten home run in the competition to 12 matches (W8 D4) in emphatic fashion on Tuesday.
Karim Adeyemi led the way with a first-half hat-trick as BVB led 5-1 at the break, with the forward becoming the first Dortmund player to score three goals in the opening 45 minutes of a major European game since Marcio Amoroso in a 2002 UEFA Cup semi-final against Milan.
Celtic, who equalised just two minutes after Emre Can had opened the scoring from the penalty spot at Signal Iduna Park, became the first British team to concede five goals in the first half of a game in major European competition since Cwmbran Town against Progresul Bucharest in the 1997-98 UEFA Cup Winner's Cup.
For the third time in his managerial career, after 7-0 and 7-1 drubbings by Barcelona and Paris Saint-Germain respectively in 2016 and 2017, Rodgers saw his side ship seven goals in the Champions League.
"I don't think I've been involved in a game where every mistake we made got punished," Rodgers told TNT Sports.
"It was a tough watch, to be honest. We weren't at our best. They showed why they are a top, top team. We didn't make the start we wanted.
"We went in high in confidence. We felt we were in a really good place. We had to start much better than we did, as we gave away really cheap goals. And we got punished for loose bits of play and passes.
"They were ruthless in their finishing. It was incredible to see.
"My job is to go away and inspire the players again. We need to learn from it or we will get punished at this level."
Dortmund coach Nuri Sahin, meanwhile, said his team have set a "benchmark" for their level of performance moving forward, after what has been an inconsistent start to the season.
Speaking to Amazon Prime, Sahin said: "Of course I'm extremely happy, but I can also put the game in Stuttgart [a 5-1 loss] into perspective – and today.
"What makes me happiest is how the guys worked up front. Goals like that come when you run up front like that. We didn't manage that at all in Stuttgart.
"With the speed and quality up front, we’re hard to beat. This coverage, the will to win the ball, has to be the benchmark. We've made steps in our notorious development."
Dortmund matched their joint-highest victory in the Champions League, matching a 6-0 win over Legia Warsaw in 2016.
