United Kingdom, July 28 -- Geezer Butler "wasn't prepared" for how "frail" Ozzy Osbourne was during rehearsals for the Black Sabbath reunion gig.

The band got back together for one huge final show - the Back To The Beginning concert - at Villa Park in their hometown of Birmingham, England on July 5 and bassist Geezer has admitted he was shocked to see singer Ozzy in such poor health.

In an essay written for The Sunday Times newspaper, Geezer explained: "The rehearsals for that final show started a month before at a studio in the Oxfordshire countryside. Tony Iommi, Bill Ward and I ran through seven songs together. Of course, not having played together for 20 years, it took a couple of days to get rid of the rust.

"Then it was time for ...