Celtic captain Callum McGregor has issued an apology to the club's fans and insisted there were no excuses for their dismal display in Dortmund.

Ruthless Borussia Dortmund put the Scottish champions to the sword as they dished out a 7-1 thrashing at Signal Iduna Park on Champions League Matchday Two. It's the third time Rodgers' Celtic team have shipped seven goals in a Champions League encounter The 31-year-old skipper is adamant that lessons have to be learned on the biggest club stage of all to prevent further crushing defeats.

The Celtic squad, management and staff made a point of acknowledging the 4,000 Celtic supporters who had travelled to Germany for the match as they lingered long after the final whistle to show their appreciation. McGregor said: "We can only apologise to the fans because when you play for Celtic and get beat 7-1 it is not good enough. Credit to them for sticking with us and we thank them for that. We know that can't happen again. Thanks to them for sticking with us.

"I hate standing here making excuses when you lose heavily like that but I have to say a word about the supporters because all credit to them as they stuck with the team and that is a compliment to how well the team is playing and how well the season has started.

"Everybody will have a pop and that is what happens when you play for Celtic. I hate trying to make excuses when you get beat 7-1 because it is not acceptable. There are still positives because the season has started well and in the game against Slovan Bratislava we were excellent. It shows you what this level is like when you don't quite play to it and they have a good night. That made things difficult for us.

"We came and we wanted to be aggressive in the game and we have been humbled a bit. We are on a learning curve but we need to be better for the games that are coming up and understand the level we are competing at. We need to bring a better level of football game than we did against Dortmund. We also need to learn that when the game starts to get away from us we can shut up shop a bit and steady the flow of the game for five minutes.

" It is not all doom and gloom but there are no excuses when you lose 7-1."

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(Image: Alan Harvey - SNS Group)

McGregor admitted that last season's Champions League runners-up were one of the best European sides he has ever played against after putting Celtic through the 'spinner' in a relentless first 45 minutes that saw the hosts go in 5-1 up at the interval.

McGregor reckons Celtic could learn a thing or two about how a top club renowned for playing attractive attacking football operates at this level. However, he firmly believes qualification for the knockout phase it still within Celtic's grasp. He said: "You have to give credit to them they were clinical and the edge that they showed in the game. We lost the game in a 20-25 minute spell where we are in the spinner a little bit and struggling to get a grip of things.

"In the second half, we tried to steady it but we lost goals in transitions. I think all in all it was a sobering night for everyone. It is never nice to lose a game of football 7-1 but we are where we are and where we expected to be after two games. It is a bad result and we have started the season really well and we just need to stay together.

"Borussia Dortmund were excellent. They were really good. They had huge speed at the top of the pitch. They had great ideas and good technical players who could execute the game that they were looking to play. The level of finishing was outstanding. It is difficult to change the mindset as you want to be aggressive as that is the way we play and that is in our DNA. It is just drummed into us for so long that we think the best form of defence is attack but when you are playing against this level of quality player then they have shown us that there are other ways to do it.

"We don't need to be so aggressive, especially when the game is turning against you. It is just something we have to learn from. We want to maintain that aggressiveness as we got a good result at home and we want to be aggressive throughout the tournament but we reached a level against Dortmund where they were much better than us. I think it is difficult when things go against you, and you realise on the pitch how difficult the game is. At that point, we need to be a little bit tighter and a bit more together. I think we went a little bit individual and we worried about our own space and it just opened up the game.

"When you play with players of that quality then half a yard is too much and you see the quality they have got. It is difficult when the game gets away from you but it is something we need to try and learn from for sure. We spoke about the positives from the first game so you have to address this and we spoke about trying to steady the flow at half-time and we did that for large parts in the second half but the other two goals kill you a bit.

"We have got a bit of work to do in the next six games and if we manage to get to where we want to be it has been a worthwhile exercise as it is a learning curve with the group."

McGregor insists Celtic cannot afford to dwell too much on European matters as they have an important Scottish Premiership outing against Ross County in Dingwall on Sunday where they hope to make it seven league wins out of seven.

He said: "We have to quickly get over it as we have another game on Sunday and the only way we can put that right is by winning."