Celtic’s defeat in Rotterdam was particularly frustrating for me given the low expectations going in. At half time, the match was utterly 50/50 by the data and hope had started to rise:

If anything, given Celtic were the away side, you could argue based on the performance data, they’d have been the happier side.
But of course, of was 0-1 at that stage.
Goal One
Regular Huddle Breakdown listeners will know of my “three and out” theory. Do three things wrong in the defensive third and you will likely concede a chance of not a goal.
The Feyenoord free kick is over 30 yards from goal, and I can’t say I was concerned.
Then:
The on-field leadership places Kyogo Furuhashi at the inside of the wall. As Martin O’Neill commented at half time, you need your biggest lump in that position not your smallest. That’s down to Joe Hart and Callum McGregor in terms of organisation.
Kyogo turns his back and effectively jumps out the way of the ball. Basics.
Hart is slow to move his feet and despite the ball starting off a good few yards inside the post, and bouncing, and that he got both hands on it, he couldn’t keep it out. He doesn’t even take a negative step the wrong way, in fact he anticipates the ball’s direction and still cannot get across. He should expect the wall to not be breached but equally it is a long way out and not hit particularly hard or into the corner.

The third point is a function of his lack of ability to move like a younger man. Who knew? Funny how systemic weaknesses come back to bite you in the biggest games against the best opposition.
Hart has conceded six goals against post shot xG of 6.04 so effectively on par for the season. However, his obvious physical decline does not scale to Champions League level when it is stressed the most. Yes, he saved a poorly struck penalty, but the damage had been done.
Sending Off One
Brendan Rodger’s was magnanimous post-match and took the Gustaf Lagerbielke sending off on the Mowbray. It probably is an unnecessary intervention by the young Swedish defender yet the theatrics that generated the award of both a penalty and the double whammy of a red card was an extraordinarily harsh sentence for a minor misdemeanour.
But why did that situation arise?

When Calvin Stengs receives the ball wide right, Celtic’s shape is ok. The back line is aligned and McGregor and Matt O’Riley are double pivoting to allow Odin Holm to have pushed on as they had been all match.
McGregor is pushed out wide but still, it is well short of halfway.

The six foot plus 24-year-old powerful and pacy central midfielder blasts past 5’8” 30 year old slightly pace declining Scot and gets to the edge of the box unhindered. McGregor has made up the ground but not in a way that allows him to influence the play.
Stengs feeds in Paixao and Lagerbielke tries to be belts and braces with his defending and the belt wins.
Celtic being out paced and powered in midfield? Who knew?
The Naivety Narrative
Lagerbielke’s efforts and holding off the Feyenoord attacker could be branded naïve. And Holm’s out of control challenge to receive a straight red was utterly brainless given the context of just losing a man but having the lift of a penalty save. Lazy journalism has labelled Celtic’s defeat down to those incidents.
However, both debacles came after the Celtic system, with its known and undealt with risks, couldn’t scale to this level of competition.
It was such a frustrating waste.
Here is the xG and Packing Score timeline:

Until the mid-60s minutes, it was a coin flip. Would their frustration have grown; would Celtic’s confidence have grown?
We’ll never know but Celtic got into that situation mainly due to weaknesses that went unresolved in the Summer.
Systemic weakness trumps naivety every time.