The Paranoid hitmakers reformed last year (12) and in May (12), they played their first gig since 2005, with stand-in sticksman Tommy Clufetos.
Ward has previously cited contract issues for his decision to shun the reunion, but frontman Osbourne has now alleged the musicians were left aghast when they rehearsed with Ward because his playing was so rusty he relied on bullet-point notes stuck all over his kit.
Osbourne tells Mojo magazine, "I guess it's to do with finances or something... But there was also another side to it. When Bill came along we all had to ask, 'Can he do an hour-and-a-half, two-hour gig? Can he cope?' My suggestion was that we run through a set and see how he got on because he was so out of condition and the drummer is the most demanding job in the whole band.
"We looked at Bill and he couldn't remember what the f**k we were doing. But he didn't come clean and say, 'I can't cut this gig but can we work something out, guys, where I'll come on but with another drummer backing me up?' Or, 'I'll come and play a few songs', that would have been cool.
"I get where he's coming from, though. His pride was hurt and I get it. I really do get it. The guy will always be a dear, dear friend and a brother to me, but you either s**t or get off the pot... He can't be surprised that he didn't get the gig. He can't be! F**king hell!
"You know them yellow f**king stick-on memo notes? He had them all over his f**king drums. I was like, 'What the f**k's that for, Bill?' He said, 'I can't remember what I'm doing.' I go, 'How are you gonna remember out of those 500,000 bits of paper stuck all over your kit, which one you're looking at, Bill?' (He said) 'I'll know.' Ah, Ok great. I'm not gonna give Bill a hatchet job, but at the same time we haven't got the patience to deal with it."