A Green Brigade banner was also on display in the away end at Atletico’s Metropolitano Stadium despite the group’s recent ban from attending matches.

Celtic have been stressing for weeks that “political messages and banners” were not welcome after “Free Palestine” and “Victory to the resistance” flags were initially held aloft.

Shortly before kick off for the entirely one-sided Champions League fixture, at least 10 Palestinian flags were once again held up. On a miserable night for the Scottish Premiership leaders, Celtic were eventually thumped 6-0 by a vastly superior Atletico side.

On the pitch and Celtic were heavily second-best, a fortnight after earning an entertaining draw against the Spanish side

Earlier, reports had emerged of tensions between supporters in Madrid – although there was no suggestion clashes were related to Palestinian protests.

Mark O’Donnell, 61, told the Glasgow Times he had been taken to hospital after rival fans stormed a pub in the Barrio of La Latina district.

O’Donnel said he was watching earlier fixtures on television with his two sons, Michael and Christy, when around 20 rival fans entered the premises. One of the attackers is alleged to have asked, “Are you Celtic?” before the group started throwing punches.

“I have cuts to my leg and hands, Christy has cuts to his head and Michael had cuts to his hand and received eight stitches,” he said. “Michael met another man in hospital older than me who was also attacked. He had been hit in the face with a bottle and had to have numerous stitches to his face.”

More than 3,300 Celtic fans had made the trip to Madrid for the encounter, which according to reports in Spain, had been deemed “high risk” by authorities.

Last week, Celtic had banned the Green Brigade from attending matches after the group defied the club’s stance on political gestures. The ultras group traditionally organises a tifo – a choreographed display involving a large banner or image – but has been waving Palestinian flags instead recently. The group had been handing out Palestinian flags, which were waved around Celtic Park for the previous 2-2 draw against Atletico.

Maeda saw a yellow card upgraded to red following a VAR review midway through the first half at the Estadio Metropolitano, but Rodgers felt referee made the right call initially.

The Japanese attacker dangled a leg in a 50-50 challenge with Mario Hermoso, who hurt himself as he followed through.

Celtic were already trailing to a deflected strike from Antoine Griezmann and Atletico took full advantage of the numerical superiority. Griezmann and Alvaro Morata both struck doubles, while Samuel Lino and Saul Niguez also scored as Atletico hit a string of spectacular second-half goals.

Rodgers said: “I think the red card is a big turning point. We started well, started with confidence, got into some really good areas. We then get a man sent off early, which was a huge disappointment because I didn’t feel it was a red card.

“When you watch the re-run, both players kick each other’s feet. The referee saw that in game time and then he is asked to look at it.

“The first image he sees is not representative of the actual challenge. You plant a seed when the first image he sees is Daizen Maeda’s foot up, but that wasn’t the challenge and it’s a really, really soft red card.

“For a team coming here with 11 against 11, you would need to be at your real max to get something out the game and losing a man early, it becomes a real challenge and we tire and they scored some fantastic goals.”

Rodgers was angered by the reaction of the Atletico bench after the Maeda challenge, with boss Diego Simeone and six or seven colleagues racing into the technical area to remonstrate.

He said: “They will play the game, they are obviously trying to get our player sent off.

“Listen, it’s still up to the ref. You come away in Europe and a place like this where it’s an emotional stadium, everyone will add pressure.

“The ref saw it in game time and didn’t deem it worthy of anything so serious, but it just feels like a computer game now, football. So many visits to the screen, so many influences in the game.

“As time has gone on you see the influence of VAR and the difficulties referees have. There’s a lot of judgements going on away from the field.

“It’s not so much the technology, but how it is implemented. It’s not something I enjoy.

“When it first came out I was very much wanting to support it and hoped it would improve the game, because I think everyone thought the utopia of VAR would mean we would lose all these bad decisions.

“But you could argue there’s even more now. There’s a good percentage where it just doesn’t feel right in the game.”

Rodgers maintained a 4-3-2 formation after the red card, with Oh Hyeon-gyu coming on at half-time.

“You have seen my teams enough back home,” he said. “Whenever we lose a man it’s having that structure.

“Listen, you can have any structure you want, it can be very, very difficult against that level of opponent. It just didn’t work for us so we have to take our medicine.”

Celtic remain bottom of Group E but are still not eliminated from the Champions League, although they will need to beat both Lazio and Feyenoord and hope Atletico do them some favours to stay in Europe beyond Christmas.

Rodgers said: “We knew we had to take something from this game, but with Lazio winning as well, our objective with two games to go is to get points and see if we can improve on last season’s points total.”

The 31-year-old midfielder has struggled for form and fitness in his second season since his eye-catching switch to Old Trafford from Real Madrid.

Casemiro sustained an ankle injury on Brazil duty last month and returned against Newcastle last Wednesday, only to be taken off at half-time of the 3-0 Carabao Cup defeat.

United confirmed the Brazil international had sustained a hamstring that would keep him out for “several weeks”, but Ten Hag has now suggested the midfielder may struggle to play again this year.

Left-backs Luke Shaw and Tyrell Malacia may return in the coming weeks but Casemiro and Lisandro Martinez, who is out with a foot injury, are set to miss the 10 matches before Christmas.

“I have some time schedules, yeah,” Ten Hag said. “But it’s always difficult to project that because there can always be setbacks during the rehab period.