Neil Lennon could not hide his frustration with his Celtic players after defeat to Ferencvaros ended their hopes of reaching the Champions League group stage.
The hosts were behind to the Hungarian champions inside seven minutes at Celtic Park and, despite pulling level at the beginning of the second half, Ferencvaros struck again 15 minutes from time to send Celtic into the Europa League qualifying rounds.
Celtic have repeatedly struggled to negotiate Champions League qualifying games, losing to AEK Athens and Cluj in the past two seasons, and Lennon was furious with his side's performance at both ends of the pitch.
"I'm devastated," he said. "It shouldn't happen. It's a poor result and we dominated the game. We had so many chances but we conceded two really poor goals. We all have to take responsibility for it. I have to take responsibility in terms of the team selection but we had more than enough chances to win the game twice over.
"For the first goal, only [Scott Brown] is getting out to close the shot while the second one is an individual error which we should've dealt with comfortably.
"It was a basic mistake. We're making basic defensive mistakes and sometimes you can't legislate for that. We did the same against Copenhagen when we were on top. Hatem Abd Elhamed was in a decent position and all he had to do was deal with it but he doesn't. But in the final third we should've done better as well as we had so many chances to score."
Celtic have already dropped points in the Scottish Premiership this season, too, and Lennon criticised his side for over-confidence and said they must step up their levels.
Some of their attitudes need to be better. I'm just detecting a bit of malaise sometimes among them and they're not as good as what they think they are.
"The players need to buckle up," he said. "They've been OK but some of their attitudes need to be better. I'm just detecting a bit of malaise sometimes among them and they're not as good as what they think they are.
"We need to analyse where we went wrong and focus on the rest of the season."
Lennon: Some players want to leave
Lennon also revealed after the match some players had spoken to him about a desire to leave the club during the transfer window. The Celtic boss said he would not stand in the way of anyone who wants to play elsewhere and insisted he only wanted players committed to the club in his squad.
"There are some players who may want to leave and have made in-roads into that over the past six months or so," he said. "If they don't want to be here then we'll have to do something about it.
"If they're making waves to leave the club then they're obviously not committed and I want players who are committed to the club."
Brown: Every player must give 100 per cent on the pitch
Celtic captain Scott Brown insists any want-away players should still be giving their all while they are at Parkhead.
"For me, the lads want to be here," he said. "I don't know what people have said to him [Lennon] individually to be perfectly honest.
"But at the end of the day, it doesn't matter if they want to be here or not, once they go on that park, everyone gives 100 per cent, that's what the gaffer demands."
Asked if he hoped any unhappy players would speak to him about their situation, Brown said: "Yeah, definitely.
"I hope everyone wants to be here. For me, it is a fantastic club.
"There is a lot of lads who love this club that want to see us winning games, that have been here throughout, winning trophies, winning trebles and we know the feeling and it means so much to us.
"But for now, if people don't want to be here, it's hard.
"But it's not up to me whether they stay or not, that is [for] the manager and the board and that's a discussion with the players that don't want to be here."
Analysis: Lennon's gamble didn't pay off
Sky Sports pundit Andy Walker was critical of Lennon's team selection after the match.
The Celtic boss was without injured striker Odsonne Edouard but went with Ryan Christie instead of strike option Patryk Klimala.
Walker believes that accounted for Celtic's lack of potency in the final third and reckons the result - which will hit the club financially - could have ramifications in the transfer market if they have to sell key players to raise funds.
"The story of the game is that Lennon gambled with his team selection," said Walker. "Edouard was injured and what a difference to the team he makes. He didn't play and Lennon went with four midfielders as his front four. There was no recognised striker despite having Albian Ajeti, Ismaila Soro and Patryk Klimala on the bench.
"It's a massive victory for Ferencvaros as they do not compare to Celtic in terms of their budget. This is a huge disappointment to Celtic and their supporters. It is Europa League football for them, and the gamble of not playing with a striker has not paid off for them.
"Celtic couldn't have asked for better luck of the draw to get to the group stages, playing both their qualifying rounds at home. Ferencvaros were very smart, getting the early goal and then defended deeply. Celtic lacked the killer instinct inside the box and that was down to the fact they had no strikers on the pitch for around 70 minutes.
"It was all a bit powder-puff around the box and these games define your season. The pressure could now be on Celtic to sell one of their players - who knows, even Edouard who is already attracting interest from some of the big clubs in England. It's such a huge blow for everyone who wanted Celtic to go through."
Celtic host Motherwell in the Scottish Premiership at 3pm on Saturday. Lennon's team are likely to enter a one-legged Europa League third qualifying round tie on September 24, although they could be one of two teams drawn to go straight through to the play-off round. The draw takes place on Tuesday.