Celtic captain Scott Brown has acknowledged his mistake in being sent off against Barcelona on Tuesday.
The midfielder was shown a red card a minute before the hour mark in the UEFA Champions League tie after kicking Barcelona forward Neymar.
Cesc Fabregas got the winner 17 minutes after his dismissal to move the Spanish side top of Group H and Brown admitted that the red card left the Scottish champions with an uphill task.
"I realise that I made a mistake in getting sent off," he said. "It's something that happened in the heat of the moment but I shouldn't have acted in this way," he told Celtic's official website.
"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 defeat sees Celtic sit bottom of the group, having been beaten 2-0 by Milan in their European opener.
However, Brown felt that his team-mates deserved more from the game and remains confident that his side can qualify for the knockout stages.
"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," he continued.
"We have four games to go in this group and everyone in the squad firmly believes that we can still qualify, and we are determined to get our first points on the board against Ajax in two weeks' time.
"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."
|5||V. van Dijk|
|Coach: N. Lennon|
for A. Stokes 70'
for M. Lustig 70'
for K. Commons 86'
|League Two Preview: Shrewsbury, Wycombe and Burton vie for year-end top spot|
|Mancini not expecting big-money signings at Inter|
|Tottenham v Manchester United: Carrick expects tough return|
|Pearson eager to see Leicester resolve|
|Newcastle United v Everton: Martinez demands clinical touch|
|Liverpool v Swansea City: Rodgers backs returning Mignolet|
|Bayern can still improve - Sammer|
|Warnock sacked by Palace|
|Aston Villa v Sunderland: No club too big to go down, says Lambert|
|Hull City v Leicester City: Pearson vows to keep going|
|Stoke City v West Brom: Hughes targets elusive back-to-back wins|
|Rodgers dismisses Balotelli exit rumours|
|Modric will not rush Madrid return|
|Dyche pleased with Vokes return|
|Southampton v Chelsea: Koeman vows to go on the offensive|
|A-League Review: Six-goal Gosford thriller, Victory leave it late|
|Manchester City v Burnley: Pellegrini warns against complacency|
|Dortmund can fight on two fronts - Watzke|
|Sterling hails improved Liverpool belief|
|Rosicky eager to build on QPR winner|
|Wenger: ´We made it hard for ourselves´|
|Kane: Spurs eye top four|
|Di Maria in doubt for Spurs clash|
|Ba left out of Senegal AFCON squad|
|Redknapp frustrated by penalty call|
|Wenger sees Giroud wrongs|
|Premier League schedule a ´disgrace´, says Poyet|
|Championship Review: Bournemouth stay top, Heskey scores on Bolton debut|
|Hughes lauds Bojan performance|
|Koeman: Saints marching on|
|Pardew rues referee error|
|Arsenal 2 QPR 1: Sublime Alexis secures the spoils|
|Martinez questions Walters decision|
|Poyet laments Sunderland mistakes|
|League One Review: Swindon cruise to win over Walsall|
|Irvine aware of need for improvement|
|United still doing ´very bad things´ - Van Gaal|
|Lambert proud of players despite Swansea defeat|
|Warnock bemoans Palace defence|
|Bruce hails Hull´s spirit|
|Pochettino relieved to come away with victory|
|Dyche: We had our pocket pinched|
|Monk hails Fabianski performance|
|Pearson demands greater concentration from Leicester|
|Kompany set for City return|
|Rodgers hails character after battling win|
|League Two Review: Ainsworth frustrated by Luton, Shrewsbury go top|
|Everton 0 Stoke City 1: Lacklustre Everton slip to defeat|
|Sunderland 1 Hull City 3: Triumphant return for Bruce|
|Burnley 0 Liverpool 1: Sterling wins it at Turf Moor|
|Leicester City 1 Tottenham 2: Eriksen piles misery on Pearson´s men|
|Manchester United 3 Newcastle United 1: Rooney extends hosts´ streak|
|West Brom 1 Manchester City 3: Three and easy for in-form champions|
|Swansea City 1 Aston Villa 0: Hosts break Boxing Day duck|
|Crystal Palace 1 Southampton 3: Mane marks return with star performance|
|Allardyce upbeat despite defeat|
|Van Dijk happy at Celtic - Deila|
|Table-topping Chelsea delight Mourinho|
|Chelsea 2 West Ham 0: Mourinho´s men ease to victory|
|Suarez enjoying Messi, Neymar link-up|
|A-League Review: Garcia rescues point for Perth, Adelaide up to second|
|Poyet calls for mid-season break|
|Van Gaal rules out Januzaj move|
|Rodgers: Balotelli may have to get used to bench|
|Lallana: I was trying too hard|
|Walker juggles music, football careers in Sweden|
|Song to face ´brother from another mother´ Fabregas|
|Adriano announces Le Havre deal|
|Pardew braced for Old Trafford test|
|Lescott unfazed by City reunion|
|Tskhadadze appointed Georgia coach|
|United to finish top three - Ferdinand|
|Allardyce: Stamford Bridge stalemate saved my job|
|Southampton need three January signings, says Watson|
|Liverpool can make Champions League, says fanzine editor|
|Walsh: Hull clash crucial for Leicester|
|Toure, Aubameyang and Enyeama make shortlist for African gong|
|Docherty backs Chelsea to win two-horse race|
|Liverpool could benefit from Hyypia influence - Scales|
|Saudi Arabia name Asian Cup squad|
|Forty-year-old Cahill no problem for Postecoglou|