Arsenal have been the standout performers of the Premier League this season but an injury to Mathieu Flamini threatens to undo all their hard work.
The Gunners have shot in to prominence this season and top the Premier League by two points after nine games.
A lot of the credit has gone to new signing Mesut Ozil and a resurgent Aaron Ramsey but the contribution of Flamini must not go unnoticed.
His outstanding determination, fitness and natural leadership has steadied Arsene Wenger's patched up Arsenal side, who have expertly guided their way through an injury crisis.
There is no coincidence that both of Arsenal's losses this season occurred when Flamini was absent from the team.
But with a run of tough games on their way and L'Equipe reporting that Flamini will be out for three weeks with a groin injury, it seems that Arsenal are facing a stormy Autumn.
Arsenal's developing style of play has been the main factor in their success this season. By allowing them more possession, the Gunners invite their opponents forward before exposing them on the break.
With exceptional fitness levels, they have been highly successful but allowing opponents more possessions means Arsenal have had to be defensively disciplined.
That discipline has been brought by Flamini, who's exceptional positioning and organisational skills protect the back four whilst the opponents attack.
Although Mikel Arteta filled this role for Arsenal last season, he doesn't have the pace or the fitness to keep solid for 90 minutes - a fact exposed against Borussia Dortmund.
They now face Chelsea, Liverpool, Borussia Dortmund and Manchester United over the next month across three competitions. Lose them all and they are effectively out of contention for the Champions League, Premier League and the Capital One Cup.
All of these teams have exceptional attacking quality. Chelsea's main threat comes from the likes of Oscar and Eden Hazard in midfield whilst Liverpool and Manchester United both rely on their attacking talents to mask defensive frailties.
As Arsenal won't be as solid defensively, they will have to change the tactics that have worked so well, meaning the players will be dealing with different demands from Wenger, inviting confusion and misunderstanding.
Their frailty without Flamini was highlighted by Crystal Palace - the team that sit rock bottom of the league. On another day, Palace would have equalised and left with a deserved point. Arsenal got lucky but against the elite of Europe, their luck will run out.
So Arsenal fans will be hoping Flamini's injury isn't as bad as L'Equipe believe it to be. Because if he misses these key games, he could be returning to the squad in late November, picking up the pieces of Arsenal's shattered season.