Francis Rossi feels Rick Parfitt "died" months before he actually passed away.
The Status Quo rocker - who died from sepsis in December 2016 - suffered a heart attack in Turkey while on tour in June that year and his bandmate doesn't feel he was ever the same after the medical emergency.
Francis said: "His sons don't like me saying this but he wasn't the same [after the heart attack].
"For me, he died on the floor in that hotel in Turkey. "When I saw him in hospital, he thought it was 1984.
"He said he was putting a new band together with John Edwards who'd just played on his solo album. "He'd done that album in the 80s. I thought, 'Oh s**t, he thinks it's 1984.'
"Sometimes though, the old Ricky came back.
"He phoned John one day and said, 'I'm sat on my sofa naked, watching sport on the telly.'
"That was Rick all over - naked, on the sofa, watching TV."
And the 69-year-old singer doesn't feel the friend he remembered was still "there" before he died.
Asked if he misses Rick, he told MOJO Magazine: "I miss who he was, but the bloke I loved wasn't there any more."
Last year, the 'Down Down' hitmakers went back on the road, with Richie Malone stepping in to replace Rick on guitar, and Francis felt they had made the "obvious choice" with the musician.
He said: "Rick heard Richie play and said, 'S**t, he's good isn't he?' He was the obvious choice.
"I'm not sentimental, probably because I was bred to go into retail.
"One of my relatives owned most of Deptford.
"When he died, the rest of the family were dividing up his business at the funeral - 'OK, you can have numbers one to 37 on Friendly Street...'
"That's how it was. The show has to go on."