Ex-Celtic captain Billy McNeill has paid tribute to ex-team-mate and fellow Lisbon Lion Jimmy Johnstone, who died on Monday from motor neurone disease.
The duo were in the side that won the European Cup in 1967 and McNeill said: "Jimmy was a lovely wee man and was a team-mate and a friend to all of us.
"I was lucky enough to play alongside him but I have as much respect for the courageous way he handled his illness.
"He loved the Celtic fans. This news is devastating for everyone."
Tommy Gemmell, who was also in the Celtic team that beat Inter Milan in 1967, said Johnstone would go down in history as the club's finest ever player.
"It's a tragedy. We've lost a great pal and a colleague," said Gemmell.
"He fought the disease with great courage and he stood up to it well.
"On the pitch he had the heart of a lion and the ability of a maestro. He was an unbelievable player, as good as any you will see.
"We have lost a magnificent player who created a lot of history for the club. I doubt very much if we'll see his like again."
Another ex-team-mate, Bertie Auld, said he could not believe Johnstone had passed away.
"I still can't get to grips with the news. You know what a player he was, but what a person. He was the kindest guy in the world," said Auld.
"All the time he was lying there he never complained. I saw him on Friday and, like any time you met him, you left feeling a stronger person.
"Jimmy was so desperate to help other people with the same disease, he wanted a cure for it even though he knew he couldn't be helped."
Former Scotland winger Pat Nevin says he copied Johnstone's style of play when he was learning how to play the game.
"I never met him, but my dad got a book signed by him and wrote a message in it that was positive about how I played, which meant a lot," Nevin told BBC Sport.
"My dad used to watch Celtic train and study his methodology, then tell me and I would practice with that in mind."
Lou Macari broke into the Celtic side in the 1960s and he said Johnstone was a fantastic role model for youngsters.
"It was wonderful to have played alongside Jimmy and he looked after me," said Macari.
"He trained well, worked hard and had a great attitude towards the game.
"All football fans should watch the television over the next few days just to see how good he really was."
Former Rangers and Scotland defender Sandy Jardine says Johnstone's death will be mourned by fans of Celtic's bitter rivals too.
"There is a huge rivalry between both clubs but everybody appreciates quality players," said Jardine.
"Celtic fans mourned Jim Baxter and I have no doubt there will be a lot of Rangers fans mourning Jimmy Johnstone."
Celtic manager Gordon Strachan said Johnstone would never be forgotten.
"Jimmy was a wonderful player and a wonderful character and we will always have the memories - they will never die," said Strachan.
"He radiated. If you were down he made you feel better, that's the kind of guy he was. He was a great advert for Scotland."
Captain Neil Lennon added: "He was an entertainer, so exciting. He used to come into the dressing room and he never had a bad word to say about anyone."
Rangers tributes were also placed at Celtic Park
Celtic chief executive Peter Lawwell said it was a very sad day for the Parkhead outfit.
"It is a sad time for the whole Celtic family," said Lawwell. "Jimmy was rightly regarded as the greatest ever Celt.
"Our thoughts are with Jimmy's wife Agnes and his family and friends."
Like Johnstone, modern-day Bhoys legend Henrik Larsson wore the Celtic No.7, and the Swede paid his own tribute to the former Scotland winger.
"It's hard to find words that express how I feel at the moment," said Larsson, now with Barcelona.
"I didn't understand what an honour it was to wear the same number jersey as him when I first arrived at the club, but by the time I left I knew exactly why it was so special.
"Most people will remember him as an incredible player, but to me and a lot of other people it was just as important that he was a really fantastic guy."
Celtic fan and rock star Rod Stewart knew Johnstone personally.
"He was the reason I became a Celtic fan in 1971," Stewart told BBC Sport.
"We were doing some concerts in Scotland and he dragged me along to a game.
"At the end of his life, he couldn't move his body, but that face still had a beam on it."
Fellow rocker Jim Kerr, lead singer of Simple Minds, was reminded of Johnstone's worldwide renown while in the USA.
"We were working on an album in LA when a Russian tax driver asked about the wee fella with the red hair," he said.
"We are a wee country who love people who punch above their weight and Jimmy Johnstone was a wee treasure."
Scotland legend Alan Hansen told BBC Sport Johnstone was one of the finest footballers ever to play the game.
"Jimmy Johnstone was one of the best players you will ever see," said Hansen.
"Celtic fans will still remember the night he tormented Leeds at Hampden Park in a European Cup semi-final in 1970 - one of the finest club sides England has ever produced.
"He also did it against a world-class full-back in Terry Cooper who was at the peak of his career."
A Scottish Football Association statement said: "Jimmy Johnstone was a legend, a unique footballing talent who was a superb entertainer, the finest of his generation.
"He had his run-ins with authority, both at club and international level, but he was simply too good to leave out of any side. He will be sadly missed."
Glasgow Lord Provost Liz Cameron added: "Jinky was loved and admired by millions of football fans.
"His death, after a tremendously brave battle against an awful illness, will be mourned not just in Glasgow, but in cities and towns all across the world.
"This is a very sad day indeed."