The 4-1 defeat to Legia Warsaw leaves them with a huge challenge if they are to qualify for the next round of the Champions League.
It was as poor a performance as Celtic have had in Europe in the last few years, up there with the 5-0 loss to Artmedia Bratislava.
The tie is not over but to suffer a result like that means it will be extremely difficult for them to get through now.
If Celtic play like that again, it just won't happen. They have to be far, far better to have any chance.
It all could have been so different. Callum McGregor had Celtic ahead after eight minutes but then things fell apart.
They were sloppy in midfield - even the normally reliable Charlie Mulgrew was poor. He wasn't playing well in midfield. When he went into the defence he was found wanting too.
There was no cohesion in defence and no link-up between midfield and attack.
It is fair to say it wasn't Efe Ambrose's finest performance in a Celtic shirt.
You could tell from the start that his passing was off, and his sending-off was reckless.
There was a mistake in midfield but that doesn't account for you making a challenge like that. It was needless and a deserved red card.
If it wasn't for Fraser Forster, who to be honest could have done better with the first goal, the scoreline could have been much worse.
Celtic weren't up to speed with the game, they didn't look sharp enough and Ronny will have to handle the flak now.
It was a gamble to start Jo Inge Berget. It was one that back-fired for Ronny and I am sure he will realise that it was an error on his part.
To play him in a game of that magnitude was the wrong call. He only arrived at the club a couple of days before the game and he would hardly know his team-mates.
I know Ronny was familiar with him but it takes time to settle into a team and that showed on Wednesday night.
The other thing to consider was his fitness. I doubt he would be up to speed like the Celtic squad because Cardiff haven't been back training for as long as they have.
People were questioning the team selection as soon as the starting XI was named in Poland and the surprises certainly didn't work.
Playing Adam Matthews instead of Emilio Izaguirre at left-back was a big call and maybe Ronny thought Adam would cope better defensively, but that wasn't the case.
The other big call was starting Teemu Pukki ahead of Anthony Stokes. Pukki has done well in pre-season but Stokes is tried and tested. I am sure he was disappointed not to start.
It is fine being bold with your team selection when it works. but when it doesn't it does leave you open to a lot of criticism. Your decisions are questioned whenever you lose and the spotlight is on Ronny.
When you suffer a defeat like that, both in terms of the result and the performance, people will be lining up to question your decisions.
Sometimes as a manager you have to put your hand up and admit you made a mistake.
The important thing is that you learn from it and Ronny has a chance to rectify his errors next week. It is going to be extremely difficult, but it is not impossible.
After losing 5-0 to Artmedia, Gordon Strachan's side almost turned it around at Parkhead and you only have to look back 12 months to the Karagandy game where Neil Lennon's side got through after a poor result in the first leg.
It is not impossible and we know Celtic always play better at home. They will be more on the offensive next week but the big thing is that they can't play as badly as that again at the back if they are to go through.
We can be extremely critical of the team selection, performance and result the other night but the manager and players have a chance to turn it around next week.