Brown was shown a straight red card for aiming a fly kick at Neymar after tripping the Brazilian winger when the score was goalless after almost an hour. Barcelona's subsequent winner from Cesc Fabregas left Brown carrying the can for Celtic's second defeat in the Champions League, leaving them bottom of Group H.
Celtic have no right of appeal against the red card shown by French referee Stephane Lannoy although an appeal could be lodged if Uefa's control and disciplinary body decides to apply more than the mandatory one-game suspension for violent conduct. Brown will definitely be out of the home game against Ajax on October 22. Manager Neil Lennon was irritated by the sending-off and said it was soft.
Brown described the red card as "harsh" but admitted he had been in the wrong. "I realise that I made a mistake in getting sent off last night," he told the official Celtic website. "It's something that happened in the heat of the moment but I shouldn't have acted in this way.
"I still think it was a harsh decision. However, I recognise that I made a mistake and put myself and my team-mates in a difficult position. I need to live with that and there is no-one more disappointed than me about losing the match. There wasn't a huge amount of contact at all, to be honest, but I have to accept responsibility for my actions - and I do.
"The team deserved to get something out of the game after playing so brilliantly and putting in so much effort against one of the best sides in the world. I was also disappointed for the supporters after the incredible backing they gave us during the game. They were magnificent once again.
"It was another fantastic performance from the lads after the Milan game and, although we've still to pick up a point from this group, we've shown we can compete against some of the best sides in Europe. We have four games to go in this group and everyone in the squad firmly believes we can still qualify, and we are determined to get our first points on the board against Ajax in two weeks' time.
"For my part, I can't wait to get back on the pitch against Motherwell at the weekend and try to help us extend our winning run in the league."
The Spanish media had an entirely different interpretation of Celtic's midweek performance, though, and there were even calls for Uefa to impose an extended ban on Brown. The popular Catalan newspaper AS accused Celtic of "kicking everything that moves". It wrote: "As the fans have a good song in them everyone loves Celtic, despite them having one of the most horrendous styles of football in Europe, based on putting 10 players in their own box and kicking everything that moves. And even when it's on the ground and isn't moving, kick it anyway for good measure. (See Brown on Neymar)."
Of Brown's red card, AS went on: "It was a clear red that should probably also have an additional ban added on, to set an example."
Marca praised Celtic supporters for giving Andres Iniesta a standing ovation when he was substituted: "The Celtic fans always encourage their players but are also friendly and respectful of opponents, which you could see with the standing ovation for Iniesta on 88 minutes. Celtic Park, despite their team losing, thundered with applause for one of Spain's most beloved players."
Gordon Strachan, meanwhile, does not feel the need to speak to Brown about his impetuosity on the pitch. The Scotland manager did, though, highlight the reaction of Neymar in the lead up to Brown's dismissal, putting it down to cultural differences.
"You've got to remember that in South America that's accepted," Strachan said. "In Britain, your mates say, 'what are you doing? You embarrassed yourself there'.
Strachan admits there is
"a devil inside" all players, but said Brown understands the responsibilities of his role as Celtic captain and the likely captain of Scotland when the national team face Croatia on October 15.
"He has faults, but he also has assets. We have all been there. We are all a devil at a football match. We have seen it and we all go 'wooah, maybe he gave the referee an opportunity. . . ' But then we are going: 'What was Neymar doing?' It is like the David Beckham and Simeone thing. You look at David, and then you look at Simeone and say: 'I thought he was supposed to be a hard man?'"