Arsenal chairman Peter Hill-Wood admits the club have not started planning for a future without Arsene Wenger.
Frenchman Wenger is just months short of celebrating 10 years with the Gunners, who he has led into next month's Champions League final.
The 56-year-old arrived in north London in September 1996 and has steered Arsenal to three Premiership titles and four FA Cup triumphs.
Hill-Wood told the Daily Star: 'We have got the best manager of all and I dread the day when he tells us he's had enough.
'There is no plan B after Arsene.
'He doesn't want international football because he would miss the day-to-day involvement of club management. He has changed the face of Arsenal, there is no doubt about that.'
Wenger has been fiercely loyal to Arsenal since arriving from Japanese side Grampus Eight, having been targeted by several major European clubs and linked with taking charge of the England national team.
Success has followed and Arsenal could begin life at their new Emirates Stadium as champions of Europe.
Hill-Wood insisted: 'I have no idea what happens when he goes. Managers like Arsene Wenger only come around once in a lifetime.
'He is the best.'
Hill-Wood admitted that Arsenal are still in the dark over Thierry Henry's future. He added: 'I'd love to say I know the answer but I don't. Like the fans, the board are waiting.'