The Celtic captain was sent off with the game still scoreless after 58 minutes for impeding Neymar before aiming a kick at the Brazilian as he lay on the ground. Barcelona took advantage of their numerical superiority to score what turned out to be the winning goal after 75 minutes, Cesc Fabregas heading Alexis Sanchez's cross beyond Fraser Forster. A second successive defeat leaves Celtic bottom of Group H and struggling to qualify for the last 16.
Lustig said Brown had been unlucky to have been sent off for the incident - Neymar seemed to make the most of minimal contact - but that the Scot had apologised for his actions anyway. "I don't know about the red card," said Lustig. "It was a yellow for the foul but I didn't see it. It was maybe a bit harsh to be a sending off. Scott said he was sorry but, like I said, it was a little bit harsh. He did apologise but he doesn't think it was a red card. He said he maybe was touching him but I haven't seen the replay."
The Swede feels Celtic could still have won the match despite going down to 10 men. "Before Barca scored, they didn't create any chances and we were in the game. Did the red card change the game? Yes, but to be fair we had our two best chances after that. The game didn't change that much but it's hard to play against Barcelona with 10 men. We created two good chances with 10 men but they kept possession well."
Lustig insists Celtic can still reach the knock-out phase but need to beat Ajax at home in their next match. "We aren't just looking at third place now. Barcelona could now take six points against Milan. We can take points off Ajax and against Milan at home. We have belief that we can do that. We have to move forward and try to get three points off Ajax in the next game."
Efe Ambrose would not comment on the red card but admitted Celtic were up against it once Brown had been sent off. "Playing them 11 v 11 is difficult and with a man down it is even more difficult. They got their chance and took it. We had a couple of chances before they scored but we never took them."
Having put so much into their first game against AC Milan only to end up with nothing, Kris Commons admitted it was frustrating to go through the a similar experience again. "We have put a lot of work in and created what might have been the better chances. But we got an unlucky decision and had 20 minutes with our backs against the wall against maybe the best team in the world. We don't want to be the team that plays really well, creates all the chances and ends up coming away with nothing. We have got to try and rectify that.
"We need to win our two homes games then go on the road and try and win. That is going to be a mammoth task."