Celtic manager Martin O'Neill led the tributes to his mentor Brian Clough, who died from stomach cancer on Monday at the age of 69.
O'Neill and his Celtic assistant John Robertson were key parts of the Forest side that won back-to-back European Cups.
"He was absolutely sensational and I don't think Brian would
disagree with us either," said O'Neill.
"He would be the first to say that he was the greatest of all time. But he was
like England's version of Muhammad Ali.
"He had fantastic charisma, unbelievable charisma. Outwardly he had this fantastic self-belief and self-confidence but in truth I think sometimes he was as vulnerable as all of us.
"One of the great myths of all-time was that he was a manager and not a coach and seldom on the training ground.
"The very fact is that every day was a coaching lesson from Brian Clough and when he did come down to the training ground for a 20-25 minute spell you'd pick up enough in that time to do you a life time.
"He coached during the course of games. His memory was phenomenal.
"John and I were lucky that probably in that spell from 1975 to 1980 he was at his very best. He was bright, he was everything. It's a very sad day I have to say."
Robertson added: "For me he is at the top of the list because of what he has
"There have been some brilliant managers but Brian Clough achieved it at two
clubs which were totally provincial, not very big and not very fashionable, yet
he went on to win two European Cups.
"As far as I'm concerned he is definitely the best there has ever been."
Stuart Pearce captained the side during the final years of Clough's career.
He told BBC Five Live: "It is a sad day for anybody connected with Nottingham Forest and probably the world of football as well. He was one of the big characters in the game. I can't name anyone bigger.
"It was a different day every day, he brought simplicity and the main thing was respect.
"I'm eternally grateful for what he did for my career. I earned 76 England caps under Brian which says it all really. He made me as a player.
"I think he was a man for all seasons. He had a reputation for being a hard task master, which he was when it was needed.
"But there were other times like when I came back from the 1990 World Cup under a bit of a cloud and he was there with an arm around the shoulder. He knew exactly what to do at the right times.
"You can talk about him for hours in terms of stories you've got but the bottom line is just go and have a look in the trophy cabinet he brought to different clubs around the country That says it all basically.
"No matter what team we played, what competition he would want to win it. I remember we took a team to Notts County for a testimonial. He played the full side only four or five days before the Cup final, but that was him.
"Football will remember him that's for sure. There's a part of Brian Clough in all of us make no mistake about that."
Forest legend Garry Birtles was a part of the Forest side that enjoyed so much success in the late 1970s and early 1980s, and was a part of the European Cup-winning team in 1979.
He said: "We thought he was indestructible.
"When I heard, it was just like a bolt from the blue. Brian's son Nigel phoned me, he was upset, I was upset and it's just been a major shock.
"When somebody like Brian Clough dies, it's hard to explain how you feel. It's like a member of your family dying."
Clough made Trevor Francis Britain's first £1m footballer in February 1979 and Francis said the master manager never treated anyone differently.
"We all took stick it didn't matter who you were, whether you cost £1m or came on a free transfer," said Francis.
"He treated everyone the same. We all had the greatest respect for him, he was a genius at what he did. I look back on my time at Forest as an honour and a privilege to have played for him."
Former Leeds striker Duncan McKenzie says football will never see anyone like Clough ever again.
"He was box office - wherever he went. He broke the mould, had a different style of management to anyone else - he was an amazing man," said McKenzie.
"He looked at the bigger picture and is probably the best manager who ever lived, it's the end of an era.
"People talk of Shankly, Paisley, Busby, Wenger and Ferguson - Cloughie is up there with them."
Former Forest midfielder Neil Webb told BBC Radio Nottingham it was a privilege to work with Clough at the City Ground.
He said: "It was a great honour to work for him, you never knew what would happen. He gave you the confidence to be better than you probably were."
Ex-Forest defender Kenny Burns added: "Cloughie is the greatest English manager ever, he saw things that nobody else could see, that was his beauty.
"Sir Alf Ramsey won the World Cup but what Clough did was more impressive."
Frank Clark, who replaced Clough as Forest boss in 1993, said: "His greatest strength was man management.
"He hadn't learned it from books, or from going on courses, he was just a natural. He had a gift of getting 100% from everyone who played for him."
Dave Mackay, who was Clough's captain at Derby, added: "He was a one-off.
"His team talks could be ferocious but he was unique - a brilliant manager who was respected by everyone who played under him. It is a sad day."
Arsene Wenger, who has seen his Arsenal team recently beat Forest's unbeaten 42-match league record, said Clough was a true legend of English football.
"I remember watching his teams play and I would say that the Forest side of the late 1970s will go down in history as one of the all-time greats," said Wenger.
"It is not an exaggeration to say that I was truly touched recently when he complimented the way this current Arsenal side plays and that we deserved to break his record.
"People use the word legend too freely but Brian Clough is a true legend of English football and his success in this country and in Europe is a legacy for which he will always be remembered."
Sir Alex Ferguson and his Manchester United side locked horns with Clough during the 1980s and 90s.
Ferguson said: "He's done something unique. He's won two leagues with provincial teams, not the big guns, and he's won the European Cup twice in a row with a provincial team.
"He was eccentric at times, but I don't think there was anything wrong with
"I quite enjoyed some of it, though I was sometimes on the end of it."