Coventry City stalwart Richard Shaw rates Roy Keane as the best player he has faced - but can understand why the Celtic midfielder is considering hanging up his boots in the summer.
The Manchester United and Ireland legend, aged 34, has hinted that hip problems could force him to retire at the end of the season.
Shaw believes Keane's absence from top-class football would be a great loss having been the driving force behind United's past success.
But Shaw can understand why the midfielder would want to put his family and health first, saying: "Having played against him for many years when he was at Manchester United, I know what a great player he was.
"He is probably the best player I have ever played against and he must be having an influence at Celtic as well.
"He was a great success at United and was the reason why they won so many trophies. He has been absolutely phenomenal, amazing.
"He makes people around him play. People like Eric Cantona and Peter Schmeichel have said what a great player and professional he was. You cannot get any higher praise than that. But I am 37 myself and I know how the body aches and creaks after a few days.
"Only Roy knows his own body and what his future holds but I am sure if he decides to stop playing it will be the right decision."
Shaw was at Parkhead to publicise his testimonial match against Celtic on April 11 at the Ricoh Arena, and was moved by the outpouring of affection and shrine made for Jimmy Johnstone outside the ground.
He knew all about the Lisbon Lion having revealed that Gordon Strachan used to play videos of his favourite player on the team bus and in the hotel when he was manager of Coventry.
"I have been taken aback," Shaw said. "I am so sorry to hear about the death of Jimmy Johnstone.
"He was somebody I never saw play having been down south and not old enough.
"But I did get the chance to see him on videos lots of times. When Gordon was at Coventry, more or less every away trip, he always put him on the coach on Fridays and at the hotel.
"In that era, when everyone used to blatantly kick, push and pull you, for him to shake them off with his skills and wizardry was unbelievable.
"I know he was Gordon's favourite player because he used to drill into us about watching DVDs of him.
"We used to grumble 'not another DVD' - but by the end of a trip we would be transfixed, amazed in silence, watching this guy.
"It's a huge loss to football and from what I hear he was a great man as well. Everybody in football is sad to hear of this death."
Shaw believes Strachan and the players will use Johnstone's passing as an inspiration for Sunday's CIS Insurance Cup final against Dunfermline at East End Park.
He added: "I have heard about them wearing No 7 on their shorts. It will be a great motivation as he was a great player for Celtic.
"Having spoken to a few supporters I know they all say he is the best Celtic player they ever had.
"I am sure Celtic will go and perform well and win the cup on Sunday in his memory."
Shaw believes that will be the first of many trophies Strachan brings to Parkhead in what will be a successful career as manager.
He said: "I just knew he was going to go on to bigger and better things with his determination to succeed as a player and manager. He played in the Premiership at 40 which is an incredible achievement in itself.
"He used to play against Arsenal, Chelsea and Manchester United and not look out of place which is absolutely incredible.
"I have no doubts whatsoever that he will be a great success here as a manager."