Alex Ferguson said Friday that it was "unthinkable" that referee Mark Clattenburg had racially abused a Chelsea player during Manchester United's controversial victory last weekend.
United's 3-2 Premier League win was overshadowed by allegations from the losers that Clattenburg, who sent off two Chelsea men, used "inappropriate language" against two of their players during the match.
It is a matter that is being investigated by both London's Metropolitan Police force and the Football Association, with the focus now on claims that Clattenburg used a racist slur against Nigeria midfielder John Obi Mikel.
A second accusation, relating to Spaniard Juan Mata, has been dropped by Chelsea while Clattenburg maintains his innocence on all matters.
Now, after words of support from Arsenal boss Arsene Wenger, Clattenburg has received the significant backing of Ferguson, the manager in the visitors' dug-out during the contentious afternoon at Stamford Bridge.
"I don't believe Mark Clattenburg would make any comments like that," Ferguson said Friday. "I refuse to believe it. I think it's unthinkable.
"In the modern climate, I just don't believe it. Simple as that. There is no way a referee would stoop to that, I'm convinced about that."
Ferguson, United boss for more than a quarter of a century, added: "I think the way we see the game today as compared to the way it was 25 years ago, it has completely changed.
"I played myself and I know the banter that goes on between referees and players 25 years ago is different from today," insisted Ferguson, who made his name in football as a striker with now fallen Scottish giants Rangers.
"I've never heard of a player come to me in the last 15 years and say, the referee swore in the game. Ever. So that's where I stand, I don't believe it.
"It's a wider (society) issue but I'm not concerned about that. You asked me a question about last Sunday and that's what I think."
United, a point behind league leaders Chelsea, returned to Stamford Bridge on Wednesday, losing an incredible League Cup tie to the London club 5-4 in extra-time and Ferguson paid tribute Friday to the role of veteran Ryan Giggs in that match.
Giggs may be coming towards the end of a magnificent career with United but Ferguson still sees him as an inspirational figure.
"I thought Ryan Giggs was an example to both sets of players on the pitch," he said. "He's approaching 39 this month -- the 29th of November -- it's absolutely phenomenal a player can produce that for 120 minutes.
"It encourages you, makes your job worthwhile, when you can see someone demonstrate that commitment to playing the game of football. So I was really pleased with that, thought that was fantastic."
After two high-scoring games against Chelsea, Ferguson said he'd been handed a headache by the form of young Mexican forward Javier Hernandez, scorer of a controversial winner at Stamford Bridge on Sunday, ahead of this weekend's clash with Arsenal.
Hernandez joins Danny Welbeck, Wayne Rooney and prolific summer signing Robin van Persie, who arrived from Arsenal, in an attacking force that has left Ferguson pondering his ideal line-up.
"We've got options," said Ferguson. "Chicharito (Hernandez) obviously is in fantastic form and obviously has given me the biggest headache I possibly could have but it's a great headache.
"The boy is improving all the time and the key to Chicharito's form this season is he has had a decent rest in the summer.
"The last three years he has played right through the summer with Mexico and it's now the first time he has had a decent rest in the summer and that has shown itself in his form this year."