Since 1997, Arsène Wenger has successfully steered his club without fail into the Champions League group stages and over those years Arsenal have benefited from the income and prestige that comes with being an established part of the elite of European football. In that time they have won three Premier League titles, signed the likes of Thierry Henry and Cesc Fabregas and built one of the best stadiums in the world.
Should they slip up tonight in north-east Italy and allow humble Udinese to claim only their third Champions League group stage qualification then, all of a sudden, the world will look a very different place tomorrow morning. Some of the lustre that marks Arsenal out as one of European football's most famous clubs will be gone and wherever they go this season, starting with Old Trafford on Sunday, the mocking chant, "Thursday nights on Channel Five", will surely follow.
The Europa League is no bad competition but it is not where Wenger, or the club, see themselves in the great European pecking order. In the short term it would affect the thinking of the players they hope to sign in this last week of the transfer window. In the longer term it would leave the club scrambling this season to make sure they are not left behind in qualifying for next year's Champions League. For Wenger, you suspect, it would be a painful personal blow.
When Wenger settled into his seat for the charter flight to Trieste yesterday afternoon, he might have been glad for a few hours peace from the demands of the job. So it would have seemed like a cruel joke had he picked up his in-flight magazine which featured a less than flattering interview with his former captain Tony Adams who has developed an unfortunate habit of late of sniping at Wenger at every opportunity. "I love Arsène dearly," Adams said, "but coaching is not his strong point."
It might seem like open season on Wenger at the moment but, however haunted he looks on the touchline, the rest of the time he does not carry himself like a man with the worries of the world on his shoulders. He was in good form yesterday. When he sat down to talk with newspaper reporters at Luton airport, he described the latest tale of woe concerning Jack Wilshere's injury, another gloomy instalment in a saga of bad news for Arsenal, before adding the deadpan postscript, "It's not ideal", for comic effect.
If the pressure is on Wenger then he does not show it, unless it is those slightly deranged moments during games when he throws water bottles or rubs distractedly at his hair. The rest of the time he is calm and jovial. By the time he arrived in Udine last night he was confidently predicting to Italian reporters that "by the end of the season there will be two or three [Arsenal] players who you don't know at the moment who will have surprised you with their quality."
The problem for Wenger is that after six seasons without a trophy a number of factors are combining to create the perfect storm around his team: the departures of Fabregas and Samir Nasri, injuries to key players, a bumpy start to the season and this awkward Champions League qualifier coupled with his reluctance to spend money on transfers. One bit of bad news seems to lead to another and Wenger's serenity in the face of crisis is no longer as reassuring as it once was to supporters.
Nevertheless, the man himself is showing no signs of panic or agitation. More than once yesterday he referred to the extent of his own experience as if to put the club's current concerns in perspective. In terms of his management of the situation, Wenger was – as ever – very impressive, even though it will be on tonight's result that he will ultimately be judged.
"It is very difficult to explain [how vital] the Champions League is for us," he said. "We want to compete with the best teams in Europe and the only way to do this is to compete in the Champions League. It had a big meaning for me, a big meaning for the players and a big meaning for the club. If you are there on a consistent level [like Arsenal] it has a big significance for you."
Earlier he had batted away any suggestion that there is a serious problem at the club. "We still have a very strong squad and that's what will be at stake [against Udinese] and in the coming weeks, and we will strengthen our squad, of course, in the coming weeks. Hopefully we can manage to do that. I believe in the players I have and sometimes, the fact that you lose big players gets the team on the edge a little bit. It forces each of them to give a bit more, fight a bit together and that's of course what we will want to show."
The weather in Udine is unseasonably hot, even for this time of year, and they have a good side. Wenger picked out the Chilean midfielder Mauricio Isla and the pace that Udinese have on their wings as threats. Arsenal got a taste of that in one run in the first half by the Colombian Pablo Armero at the Emirates eight days ago and tonight Udinese will throw everything that they have at Wenger's side.
The truth is that, even allowing for suspensions and Nasri's departure, Arsenal have a good enough XI tonight to win this game, although the same cannot be said of the team that Wenger will be able to pick for Old Trafford where he will be without the suspended Alex Song and Gervinho. What Wenger has to deal with tonight is the psychological effect on his players of the departure of yet another of their team-mates for what seem to be greener pastures.
"I am a realist so I have no illusions about that," Wenger said. "But I think it's part of the modern life of a professional football player. It's not by coincidence that everybody suddenly lands at Man City." By that he meant that they are moving for the money. But if Arsenal fail to secure Champions League qualification tonight, City will have one more advantage over them.
Three key confrontations
Antonio di Natale v Thomas Vermaelen
Arsenal's centre-back captained the side in last week's first leg and impressed in the defeat against Liverpool, and Arsène Wenger will again look to the Belgian for a commanding display against Udinese's main attacking threat. The diminutive Di Natale will be hoping to add to his 130 goals for the club as they adapt to life without Alexis Sanchez.
Neuton v Theo Walcott
A summer arrival from Gremio, Neuton struggled against the England winger on his first start for the club at the Emirates last week, allowing Walcott to move inside to open the scoring after just four minutes. A similarly slow start from the Brazilian left-back tonight could prove beneficial to Arsenal's hopes of progression, with Walcott charged with providing the visitors' attacking impetus and likely to again seek to expose the 21-year-old Neuton's lack of experience.
Mauricio Isla v Aaron Ramsey
With Cesc Fabregas gone, Samir Nasri going and Jack Wilshere out for a month, much expectation has been heaped on the shoulders of Aaron Ramsey to be the creative hub of the Arsenal midfield. The Welshman was at the heart of the move for Walcott's goal last week, providing the assist from the right wing, and will be tasked with creative work and defensive duties. Chilean midfielder Isla had an indifferent game at the Emirates and will have to improve to stifle Ramsey.