BRENDAN Rodgers has exuded a strangely confident air since his Celtic side was held to a 0-0 draw by Rosenborg in the first leg of the Champions League third qualifying round last week.

Players can sense if a manager is on edge before a big game from both his demeanour and his public statements and if they detect any apprehension it can have a negative effect on their performance.

Rodgers will have wanted his players to be upbeat as they head into their rematch with the Norwegian champions in the Lerkendal Stadium this evening.

Read more: Brendan Rodgers: Celtic will keep calm and carry on in Norway

He will, then, have consciously tried to be outwardly relaxed about the challenge which awaits them in Trondheim this evening.

The Northern Irishman, though, is no fool. Privately, he knows full well the predicament his side finds itself in. Deep down, he will appreciate the consequences of failure only too well.

This outing is without doubt the biggest test he has faced in his time at Celtic so far. If he is unable to pass it then it will be the first significant disappointment of his tenure.

Losing to Kare Ingebrigtsen’s team this evening will see his side fail to progress to the play-off, never mind the group stages, of Europe’s premier club competition.

Financially, that will cost the Glasgow club over £30 million in revenue.

The former Swansea City and Liverpool manager is, as a result of his heady achievements last season, held in as high a regard by supporters as any of his predecessors.

Read more: Brendan Rodgers: Celtic will keep calm and carry on in Norway

But he knows that in the harsh world he inhabits he is only as good as his last victory. Dropping down into the Europa League play-off will lead to inevitable criticism from fans. That will be a new experience for him.

Rodgers was castigated for playing Dorus de Vries ahead of Craig Gordon in goals, handing Cristian Gamboa his debut and switching to a 3-5-2 formation in their record 7-0 defeat to Barcelona away last term

But losing to the Catalans, Andres Iniesta, Lionel Messi, Luis Suarez et al, at the Nou Camp, even by such a large margin, was far from a disgrace. Far more expensively-assembled teams have been thrashed by similar scorelines. Indeed, Paris Saint-Germain were thrashed 6-1 later that term.

Many of those who file through the turnstiles at Parkhead in their tens of thousands every other week will not be so understanding should Celtic fail to overcome decidedly limited opponents and progress tonight.

Rodgers has certainly not had his troubles to seek in this double header. He was without his first choice strikers Moussa Dembele and Leigh Griffiths last week due to injury. He was also missing centre backs Dedryck Boyata and Erik Sviatchenko.

Read more: Brendan Rodgers: Celtic will keep calm and carry on in Norway

Regardless of how strong a squad a manager has – and Rodgers has a pool of players which is the envy of his counterparts in Scotland – that is not easy to cope with.

The 44-year-old tinkered with his formation and played Tom Rogic, who is at his most dangerous playing just off a lone striker, up front. It did not work. In fact, it was an unmitigated failure.

Having Griffiths, who was suspended as well as being unavailable with a calf injury, in his starting line-up will help Celtic’s chances of success enormously.

But if the Scotland internationalist, who has played in little more than an hour of competitive football this season, remains sidelined his manager will need to get his team selection spot on for the visitors to triumph.

Who does he play in attack? Does he give James Forrest the nod? The winger impressed up front in the 5-0 win over Sunderland at the Stadium of Light on Saturday. Does he bring Callum McGregor in? The dynamic midfielder was an unused substitute seven days ago. But he netted a hat-trick at the weekend. Does he go with Scott Sinclair? The wide man has moved from his favoured position before.

Who does he play in defence if Sviatchenko fails to pass a fitness test? Does he persevere with Kristoffer Ajer as he returns to his homeland? The 19-year-old didn’t let anybody down when he made his first competitive start last week.

Read more: Brendan Rodgers: Celtic will keep calm and carry on in Norway

There is much to ponder. If Rodgers gets it right he will be hailed, and not for the first time since he arrived in Scotland, as a tactical genius and motivational mastermind. If he gets it wrong, if Celtic don't function at their best once again, and his team is knocked out it will reflect badly on him.

After going undefeated domestically and winning only their fourth domestic treble last season improving in Europe, possibly even reaching the knockout stages for the fourth occasion, was widely seen as the natural progression for this Celtic side. Not making it into the actual competition, then, will be a blow.

Celtic have come back from worse results in continental competition in the past. In 2009 they were trailing Dinamo Moscow 1-0 and won the second leg 2-0 to proceed. Back in 2013 they were trailing Shakhter Karagandy 2-0 in the play-off and triumphed 3-0. It can be done.

Rodgers will have to coax a far superior display out of his players than the one they produced at Parkhead last Wednesday night – when only some inspired play by Gordon and some slapdash finishing by their adversaries ensured they escaped with a draw – to survive and move a step closer to the promised land of the Champions League and bank its untold riches.