Roger Penske says Marcos Ambrose has asked to temporarily be replaced as driver in the V8 Supercars Series.
Penske says the former NASCAR driver made the request so he can familiarize himself with the cars following his return this year to the series. Ambrose won the V8 Supercars championship in 2003 and 2004.
He spent six years in NASCAR's Sprint Cup Series but returned to Australia at the end of 2014 to drive for DJR Team Penske.
Ambrose's top finish in two races is 12th, and he'll be replaced in his hometown event in Tasmania by Scott Pye.
Penske said in a statement Tuesday that Ambrose "understood that the competition in this series is at a very high level and now realizes that more time is required for this transition."