The country music superstar recorded 'Redemption Day' with the iconic singer shortly before his death in 2003, and she admitted being back in the studio hearing his voice from the demo in her headphones was a career defining and emotional moment.
Sheryl - who reached out to his family about releasing the tune - told BBC Radio 2: "The weird thing about it was, was recording it in the studio with his voice in my cans, it really felt like he was so present.
That's what made me feel like 'this is my last album'. I don't want to make another sound. I want this to be the last, that leaves the taste in your mouth."
As well as The Man In Black himself, 'Threads' also features appearances from a who's who of music, including the likes of Stevie Nicks, Eric Clapton, Willie Nelson and Keith Richards.
For the 'Soak Up the Sun' hitmaker, having such an impressive roster of collaborators was a big reason her 11th record will be her final one.
She said: "It's one of the reasons that when we were half way through it, I told my producer Steve Jordan, I said 'This is going to be my last album'. Because for me, there's no way to follow it up!"
However, the 57-year-old singer's fans needn't worry, because she confirmed although she won't make another full length LP, there will still be new material being released.
She explained: "Well, I think I will continue to make music and put songs out. I don't think I'll make full artistic statements because it takes a lot of time and people don't listen to music that way anymore. They make song lists or whatever... I'm gonna be around, you can't get rid of me."