Welsh crooner Tom Jones was a popular late signing for the 2008 concert after American country-rock musician John Cougar Mellencamp withdrew because of a commitment to an induction at the Rock and Roll Hall of Fame.
In 2009, torrential rain as thousands of fans poured into the venue forced the cancellation of a concert that was to have starred American singer and songwriter Lionel Ritchie.
Promoters and the winery decided not to stage a concert in 2015, and the following year another American act, Ben Harper and the Innocent Criminals, pulled out of what was to have been the first night of a two-night arrangement as the prelude to top-billing British soul and pop stars Simply Red.
There were no hiccups last year when American country-rock queens Dixie Chicks restored the concert to its former glory.
Mr Holley said not too much should be read into the fact that a concert on-or-off deadline only 48 hours after Wednesday's announcement of the Neil Diamond withdrawal had been stretched.
"It's like a forecast for rain," he said. "There's 50 per cent probability of rain, and there's a 50 per cent probability of no rain."
"If we do have to cancel we would want to know we did our absolute best. But when you're trying to secure an act just seven weeks out, your options are somewhat limited."
Compounding the job of finding suitable acts available for the concert, which is scheduled for March 17, is the time-zone factor.
"A day in the life of some international performers might actually be two days. There would be a bit of waiting for people to get back in touch," Mr Holley said.
A number of local acts had "put their hands up," but there was no word on whether discussions include a reunion of Split Enz, who last reunited on stage in 2009.