Arsenal manager Arsene Wenger has spoken of his admiration for Sir Alex Ferguson's "remarkable" reign at Manchester United as he prepares to celebrate 25 years in charge.
"It is remarkable through the quality and the consistency," Wenger said.
The pair were once known for their fiery relationship as their sides competed for Premier League glory.
But the Frenchman admits there is now more respect between the two longest-serving top-flight bosses.
"It is exceptional as well because I don't know anybody who has done 25 years at the top level with the same club. Certainly nobody will do it again."
Wenger, who was appointed as Gunners boss in 1996, helped guide his team to the Premier League title in 1998, 2002 and 2004.
Ferguson's men have since gone on to win four league titles since 2004, with the during his long stay at Old Trafford.
Asked whether he could achieve the same feat at Arsenal, Wenger added: "The distance is a bit far, that would be 10 more years.
"I am already happy if I make this year a good season after all of this."
United had not won the championship since 1967 before Ferguson took them to Premier League glory in 1993, and the 69-year-old has since added another 11 titles.
In all, since being appointed in November 1986, Ferguson has won 37 trophies with United, including two Champions League titles.