Maynard James Keenan thinks it will take "modern miracles" for Ozzy Osbourne to perform on stage at Black Sabbath's final concert.

The Tool frontman is one of many artists who will be performing at the 'Paranoid' rockers' 'Back To The Beginning' show at Villa Park in Birmingham, England, on 5 July and having seen Ozzy - who has had neck and spinal issues, as well as Parkinson's disease, and sometimes uses a wheelchair as a result of his mobility problems - struggling at the Rock and Roll Hall of Fame induction ceremony last year, Maynard is "preparing for the worst but hoping for the best" at the gig.

Speaking to Loudwire Nights, he said: "I think for me, seeing Ozzy moving around at [the Hall of Fame ceremony], the idea of him playing a show at all, if we're being honest, the conversation about going to do the song was like, 'We'll have this conversation, but, ahh… I don't know that this [concert] gonna happen.'

"And even now, I'm cautious about saying, 'Yeah! All in, he's gonna do it.' Because man, I don't know what kind of modern miracles we'll come up with to get him on stage to do the songs, but this is gonna be a challenge for them.

"So, I'm honoured to be a part of it, but I'm kinda preparing for the worst - but hoping for the best, as they say."

Maynard first heard about the concert at the Rock and Roll Hall of Fame ceremony and was originally expecting to be part of a supergroup before Tool were invited onto the bill.

He said: "The conversation first came up when I was at the Rock and Roll Hall of Fame, hanging out with Wolfgang [Van Halen] and some of the guys, I think even [Metallica bassist] Robert Trujillo.

"We were on the travel over there, just going, 'OK, well, there's a rumour about the Black Sabbath show.' I was like, 'Well, let's do something.' So I kinda had planned a song to do and all of a sudden I'm at home and I get the call, 'Hey, Tool's been asked to do a song,' and I'm like 'F***.' Now I have to call back Wolfgang and those guys and go, 'I'm going to do it with Tool, sorry.' "