They selected the Rage Against The Machine man from a shortlist drawn up by producer Rick Rubin – which included Ginger Baker – after Tony Iommi ended negotiations with original sticksman Bill Ward over his return.
But Geezer Butler admits they thought they’d chosen the wrong man for the job at first.
The bassist tells Faster Louder: “We literally had two weeks to work with him before we recorded the songs. The first week we were going, ‘This guy’s just not working out,’ and we were panicking.
“We went into the studio and recorded the first three songs with him – and that was probably where Rick really worked out the most. He had the definite idea of what the drummer should do, so he was communicating with Brad, and he’s worked with Brad before.
“It just all fell into place. He did a great job in the end.”
Iommi recently explained how he’d carried on conversations with Ward, who said he hadn’t been offered a “signable” contract in the months after Sabbath announced their reunion. But when the guitarist was diagnosed with cancer he decided to cut talks short, fearing he was running out of time to make the album.
Butler comments: “Bill started the album with us, the writing stuff, and then we announced the reunion and everything. Then Tony was diagnosed. We all got back together after Tony’s first treatment and for some reason something had happened with Bill, the business side of it, and it just didn’t work out.”
The bassist, who wrote lyrics for 12 of the 16 tracks Sabbath recorded, found he was pressed for time himself. “I literally had to write the night before Ozzy sang them,” he says. “I didn’t have any time – but when push comes to shove it just had to be done. And I work better under pressure.”
13 is released today.