Europa League: An in-depth look at Celtic's downfall against Valencia
It may be only half-time, but already Celtic's hopes of reaching the last 16 of the Europa League hang by a thread.
A sobering 2-0 defeat at home by Valencia came as a culture shock to the Scottish champions, who went into the tie on the back of seven wins and seven clean sheets.
Manager Brendan Rodgers cursed his side's mistakes to allow the visitors to take a firm grip of the tie, also citing lapses in concentration as a factor in their downfall.
But does he have a point? Were Celtic that below par, or were they simply outdone by the side who currently sit eighth in La Liga?
BBC Scotland takes a look...
Celtic failing to go forward
The fundamental problem with Celtic's approach to the loss to Valencia was their inability to effectively pass the ball where it mattered to create goal-scoring opportunities.
According to the stats, 61% of Celtic's 790 passes on the night went forward towards the Valencia goal. That may seem like a fair return, but bear in mind that against Salzburg that figure stood at an even more impressive 72%. And against Leipzig and Rosenborg they moved the ball forward 74% and 67% of the time, respectively.
As a result, Celtic simply failed to have any presence in the Valencia final third at all. Of those same 790 passes, only 16% were made deep in the opposing half which, compared to the corresponding average across the other three home ties in this season's competition, comes out 13% lower.
Although the Scottish champions have picked up a varying degree of results over the course of their four home ties in this season's Europa League, Wednesday's game was undoubtedly an outlier when it comes to an opposing team nullifying their attacking intent.
McGregor lacked cutting edge
Rodgers spoke about Celtic losing their momentum and essentially playing within themselves once Valencia stepped up a gear.
Callum McGregor has unquestionably been one of Celtic's best players this season but the central midfielder was far from his most effective on Thursday night.
For example, only 15% of McGregor's passes on the night were made in the final third of the pitch, which is considerably less than the 27% he has averaged over Celtic's past three homes ties in Europe.
Ironically, what perhaps best sums up the midfielder's tepid nature on the night is just how accurate his passing actually was. In the 1-0 win over Rosenborg, McGregor's passing accuracy stood at 80%, while his success rate for threading passes across the pitch in the 2-1 win over Leipzig was similar at 76%.
However, that is nothing compared to the 90% return on Thursday night against Valencia, with Rodgers claiming post match his team's passing "became a wee bit safe".
"When you're at the top level you have to keep the ball and when you do give it away these top teams can punish you," said McGregor.
"We started well on the night but we lost momentum and then we started giving the ball away and then it becomes a case of teams scoring against you and you having to try and win that back and try to be positive."
'Every single member of the team was cheap' - reaction
Former Celtic goalkeeper Pat Bonner on BBC Sportsound
I've never seen Celtic pass the ball back as much. The purpose of possession is to control the game and almost work the ball forward to get into scoring positions, not to keep possession to allow the team to come and press you.
Once they press you, you've got to break that press somehow, whether that's through them or whether that's over them or whether that's down the side of them.
But you can't just keep passing the ball back across the back and back again.
Former Dundee United and Falkirk manager Peter Houston
The confidence went quickly when Celtic started giving the ball away.
Scott Brown in the first half gave three or four away. Then McGregor, who in my opinion is one of the best players in Scotland this season, started giving the ball away cheaply. Oliver Burke wasn't holding the ball in. He was trying to play it off in one.
Every single member of the team was cheap. The full-backs copped out by going back the way all the time. Not only Emilio Izaguirre, Jeremy Toljan was doing the same. That's the safety option.