The footballing world is in mourning after it was announced on Monday that Keegan had passed away at the age of 75.
A two-time Ballon d'Or winner and hero at his former clubs, Keegan's impact in life stretched way beyond the confines of the pitch.
Paying tribute to his friend and former Liverpool teammate, Thompson said: "He was such a great guy. Yes, a great footballer, but what made him different, not too many come along like him.
"We all do our signings, we all do our photographs with people, but this guy genuinely gave his time to them. People would go, 'Why is he like this? Why is he so nice? Why is he so good with his time to people?'
"That was Kevin and it wasn't just a one-off somewhere – it was throughout his whole life.
"As a player, then the way he became a manager [and] even with his after-dinner speaking, he doesn't just speak to people… he'll spend hours there just talking.
"They don't make people like Kevin Keegan any longer. He's been a loss to society as much as it has been to the game of football."
Keegan joined Bill Shankly's Liverpool from Scunthorpe United in 1971 and would go on to become an Anfield icon across his six seasons.
He scored exactly 100 goals from 323 appearances and lifted seven major honours – including the Reds' maiden European Cup on his final outing.
Thompson, an up-and-coming prospect from the youth system when Keegan arrived, was enamoured with the No.7's mentality and competitiveness.
Thompson recalled: "So that first pre-season in '71, I'm just sort of getting ready to sign professional forms and this guy has come in and he was wonderful with his application to the game and what he had actually wanted from football.
"We had a reserve game at Southport and there's maybe a few of my colleagues who remember this game. Ronnie Moran was our manager, the Ronnie Moran, and we got to half-time and it was 0-0.
"Kevin came into the dressing room at half-time and you could see Kevin was twitchy, and he just burst out and said, 'We're never going to score a goal playing like this. We're just not doing anything, we're not getting there.'
"Ronnie Moran sort of went, 'Do you think you can do better?' And he [Kevin] went, 'Yes, I can.' And he [Moran] said, 'Right, well you're going up front then.'
"We won the game 2-0, Kevin scored twice. To take on Ronnie, maybe he didn't understand what Ronnie Moran was all about, as we knew Ronnie, but it was great.
"You can bet your life Ronnie reported back and he would have gone, 'This fella's got a bit of character, he wants it badly.'"
Thompson continued: "We had a first team [versus the] reserves game. Now that game has become notorious now. The reserves always beat the first team.
"It was played on the Tuesday or Wednesday before the Saturday opener. For this time, the first team actually beat the reserves – because Kevin Keegan was in the first team.
"He was unbelievable because he wanted it so much – it was normally the reserves. I think the score was something like 6-2 and Kevin had scored a couple."
