Manchester United boss Louis van Gaal has no doubt Arsene Wenger is one of the world's best managers - but is not sure he could go 11 years at one club without a league title like the Frenchman.
Wenger, who celebrated 19 years in charge of Arsenal this week and last guided them to the Premier League title in 2004, has faced criticism over the past few days following his side's 3-2 home loss to Olympiacos in the Champions League.
Ahead of United's top-flight trip to Arsenal on Sunday, Van Gaal said of his Gunners counterpart: "I think he is doing great work.
"When you can, like (ex-United boss) Sir Alex Ferguson, stay at a club for such a long time, you have to be very good otherwise you shall not succeed.
"So I think Arsene Wenger is one of the best coaches of this world. In the same way, I think Sir Alex Ferguson is the best because he won the most titles.
"It is easy to say that, but with Arsene Wenger, when you are such a long time with one club and everybody is satisfied - the fans, the board, the players - then you are very good, believe me."
The extent to which all those mentioned are currently satisfied is up for debate.
And when asked if he thought any manager in Spain or Germany could go 11 years in a job without winning the league like Wenger, Van Gaal said: "I think you have to ask the board of Arsenal that question, not me."
Van Gaal - who had already described Wenger and Ferguson as "other types" to him in terms of their longevity in one job and his more nomadic career - was then asked if it would be enough for him to go so long at a top club without winning the top prize.
"That is difficult to answer because I have won a lot of titles," said the Dutchman, a champion with the likes of Ajax, Barcelona and Bayern Munich.
"That is my aim and I want to do it in different countries, not only in the Netherlands but in Spain and Germany and England. That is my ambition.
"As I said, I am not that type. I like to win a lot."
Van Gaal has expressed his ambition to win both the Premier League and Champions League with United.
They are currently top of the Premier League and he says they believe they can stay there this season - something that will only be enhanced with victory at fourth-placed Arsenal.
"You have to believe always in this," the 64-year-old said.
"I think the balance in our selection is much better than last year (when United finished fourth in his first term in charge), and last year we also had the chance. S o I believe in that, and the most important thing is not only my belief but that the players are believing in that.
"If we win against Arsenal, the belief shall raise a lot I think."
Meanwhile, Van Gaal has emphasised he is more than happy for Michael Carrick to play on for England as long as possible.
The 34-year-old midfielder sat out United's win over Wolfsburg on Wednesday before being called up to Roy Hodgson's Three Lions squad on Thursday.
And Van Gaal said: "He is fit enough. He is able to play for me against Arsenal. He was not really injured - it was a minor injury of tiredness.
"He is 34, so it is logical he needs more time to recover. But when Roy Hodgson thinks he needs him I am very happy for him, because he wants to play for the national team.
"He has also selected (United defender) Phil Jones, who still needs minutes, so I am happy he can do that with the England squad."