Sir Alex Ferguson has paid a warm tribute to Jose Mourinho - and feels Avram Grant has a "big test" on his hands trying to replace him.
Manchester United chief Ferguson has always held former Chelsea boss Mourinho in high regard even though the Scot has tended to come out second best in matches between their teams, feeling he can spot elements of his own character in the extrovert Portuguese coach.
Even towards the end of last season, when their rivalry hit its most controversial phase, personal attacks were kept to a minimum.
In fact, Ferguson's major complaint of Mourinho was the quality of wine he served up on his first trip to Stamford Bridge as an opposing boss three years ago.
And, aside from lamenting what he will do now with the bottle he had bought in especially for Sunday's Old Trafford showdown between United and Chelsea, Ferguson will miss not having his old foe in the visitors' dug-out.
"Jose leaving Chelsea is a disappointment for the game," said Ferguson.
"He was terrific for football and terrific for Chelsea. He brought something fresh and new to our game and I enjoyed the competition with him. I wish him well but I just don't know what I am going to do with my wine now."
Having won five trophies in his three seasons in west London, Mourinho has been one of the most successful managers in Chelsea's entire history.
He was responsible for ending a 50-year wait for a league title and many players and fans are completely bemused at why a situation has been allowed to develop which led to this week's events.
Ferguson opted not to offer an opinion on that but he does know exactly how much Mourinho has done for Chelsea.
"He enjoyed unparalleled success there, without question," said Ferguson.
"It is a big test for whoever replaces him - and at the moment that is Avram Grant.
"I will miss the personal challenge but what it does to them doesn't matter to me. We have to be focused on ourselves and Sunday's game.
"We are still playing Chelsea. It is still the same players and that in itself is a challenge for us.
"If you look at the record between us over the last three or four years, there is nothing in it."