Scheduling conflicts for Earl Bamber will force Kelly Grove Racing to find an alternative Bathurst co-driver for Andre Heimgartner.
Bamber was confirmed alongside Heimgartner in the #7 Ned Racing Ford Mustang for this year's Repco Bathurst 1000.
At the time of Bamber's confirmation, the Great Race was scheduled for October.
The effects of the COVID-19 pandemic have seen the race shifted to December.
Commitments for Bamber in the United States will prevent the two-time 24 Hours of Le Mans winner from driving at Mount Panorama with countryman Heimgartner.
It comes a week after United States-based Scott McLaughlin confirmed he also won't compete in the race.
Bamber made his first and only Bathurst start in 2018
The Kelly Grove squad has lined up a replacement driver for Bamber, who will be announced in the coming days.
Bamber has made just one start in the Bathurst 1000, finishing fifth alongside Shane van Gisbergen in 2018.
The New Zealander has competed in the IMSA SportsCar Championship in North America and GT World Challenge Europe.
He is also running his own team in this year's Porsche Paynter Dixon Carrera Cup series, with Matthew Payne driving the car.
"It’s extremely disappointing because I know how good Earl is having raced with him before and having seen him race first-hand," team co-owner Stephen Grove said.
Bamber finished second at Sandown in 2018
"However, there’s been a clash with the change of date for the Bathurst 1000 with his commitments in the United States.
"We’ve got a really exciting announcement who Andre’s co-driver will be, which we’ll confirm in the coming days.
"There’s no question that we’ll work with Earl to get him back next year hopefully and beyond.
"He’s an extremely good talent. We’ll definitely be bringing him back if all the dates align for 2022, no question."
Teenager Payne has been signed by the Grove Junior Team and will compete in the remaining Super2 events in 2021.
The Braeside team has yet to confirm a teammate for David Reynolds in 2022, with 19-year-old Payne mooted for the drive.
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