A bleached barnet gave Lionel Messi a whole new look inside the Aviva stadium on Dublin on Saturday evening, but it was business as usual so far as Barcelona and Celtic were concerned.

Yet, if Messi with a ball at his feet brought forth a familiar sight, so too were the Parkhead side; an Efe moment to turn a game, a striker struggling to bed in and an inability to steady a game after clawing their way back into it. It all has an accustomed ring to it.

A queue of Celtic managers before Brendan Rodgers have had just cause to raise their eyes heavenwards where Ambrose has been concerned but it has not been to invite beatific graces to fall upon him. “I think he is an unlucky guy, bless him,” said the Celtic manager with a hint of a smile. “A striker would have been proud of that goal."

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The irony is that until up he turned the ball into his own net – less than a minute after Leigh Griffiths had restored parity to cancel out Arda Turan’s opener after a Barcelona defensive howler of their own - Ambrose had acquitted himself not too badly.

He has been cast as the villain of the piece where the Celtic defence has been concerned but his part has been overplayed at times. His problem, though, his simply that while he can be assured and steady in patches, he simply cannot be trusted not to implode.

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He had a role in Barca’s third too, although better players than Ambrose have found themselves similarly red-faced. Luis Suarez nutmegged him at the byline before squaring the ball across goal for Munir to convert.

Moussa Dembele, who arrived at the club with some fanfare this summer when he became the first signing of Rodgers’ regime, is also beginning to wear the look of a player struggling for confidence. The 19-year-old former Fulham striker has yet to find the net for Celtic and the longer that goes on the heavier a weight it is to shoulder.

He did not start against Barcelona, with Griffiths once again spending a summer reiterating his credentials to remain the first choice striker.HeraldScotland: Lionel Messi of Barcelona and Efe Ambrose of Celtic. Photo by Charles McQuillan/Getty Images).

Celtic and Barcelona have met one another eight times in a competitive European context over the last 12 years, but the aim if the Parkhead side is to continue that acquaintance not in the cuddly context of a pre-season friendly, however lucrative that may be, but in the genuine environment of the Champions League.

Barcelona strolled through an encounter that lasted for 45 minutes rather than the advertised 90 – a raft of changes on both sides effectively meant the game was reduced to a training exercise at the interval – but Celtic allowed them to roll over the top of them too easily.

The pace of the game was relatively tepid for much of it, expected perhaps that it was Barcelona’s first game into pre-season and they were also without a clutch of first team players. There is no disgrace in mentioning the chasm between the teams given the vast financial disparity between them, but if Celtic are to draw anything from the encounter it is that they need to get more out of the team on a collective level.

“The players are giving absolutely everything and that has been the story from day one,” said Rodgers. “There is a lot of work to do yet but I think you can see in every game they are pressing, they are working and if we can combine that with moments of quality than hopefully that will be enough to take us through.

“We are still a long way away from where we want to be but I can’t deny the mental strength of the players. There were some real good moments in the game but the reality is there are going to be other players coming in to help the team. The attitude and energy have been first class.HeraldScotland: Celtic's Scott Brown and Barcelona's Luis Suarez battle for the ball during the 2016 International Champions Cup match at the Aviva Stadium, Dublin. Photo: Liam McBurney/PA Wire.

“You do get a taste of where you want to be from these games. You owe it to the supporters. And Barcelona don’t really play friendlies so it was a great exercise for us. We had a lot of young players involved who haven’t played against them before and I think it is a great education.”

Celtic have punched above their weight at times in the Champions League, but on the occasions they have done so they have relied upon a consistency of spirit and character. This current team still has the definite feel of a work in progress, and not just at the back where the defensive problems have been exacerbated by a lengthy injury list.

Rodgers said afterwards that he wants four new players before the window closes at the end of this month. Whether that number remains a possibility is something that the next four weeks will reveal but it was difficult not to read something of a rebuke when he pinned a definite number of arrivals to the board.

Celtic have been frustrated this summer in their attempts to bring players in purely because the English market – even at Championship level – is awash with finances that they cannot possibly compete with.

The one big carrot they have to offer could be Champions League football but there is something of a chicken and egg situation there; getting into Europe’s premier competition will generate a significant stream but actually getting their foot in the door may require quality coming in now.

The second leg of their third round qualifier against FC Astana is currently weighted in Celtic’s favour courtesy of their away goal in Kazakhstan last week, but one goal changes the complexion of the tie entirely.

Saturday’s warm-up act will have offered food for thought, but Wednesday’s night is critical to laying the foundations for the entire season.