Arsene Wenger believes Sir Alex Ferguson has set the yardstick by which every other manager has to be measured.
The Scot, 64, has enjoyed two decades of unprecedented success at Manchester United - including the treble of European Cup, Premier League and FA Cup in the summer of 1999.
Wenger has also had a major impact on the English game since arriving at Arsenal 10 years ago, securing the Double in his first full season and leading the Gunners to the final of the Champions League in 2006.
The French coach, 57, admitted what Ferguson had accomplished would take some beating.
'It is the biggest achievement,' Wenger declared.
'Of course that has to be the target for every other manager in the league, to do better than he has done.
'Who does not want to be the best?
'However, it cannot be as easy if you are the manager of Coventry to do better than he is doing at Manchester United.'
As to where Ferguson rates among the top managers in the history of the English game, Wenger reflected: 'It depends what you compare.
'If you want to count the number of championships Ferguson has won and [Brian] Clough has won, you cannot compare.
'So what Bob Paisley has won and how long Bob Paisley has been in charge and Ferguson, you cannot compare.'
The Arsenal boss declared: 'Altogether nobody has done better.
'It is remarkable to have such a consistent motivation at that level - and deal with the stress and all the other ingredients in the game.'