It is prudent we have enough cover
The British and Irish Lions on Saturday called up two replacement backs, Brad Barritt and Christian Wade, as injury cover.
Saracens' South African-born England centre will fly from the United States on Saturday and join the squad in Sydney on Monday, before travelling to Canberra.
Barritt will act as cover for Wales centre Jamie Roberts who was injured in the victory over the Waratahs earlier on Saturday.
Wade, the London Wasps wing who was scheduled to start England's second Test against Argentina in Buenos Aires on Saturday, will also join up with the squad in Sydney on Monday and then travel to Canberra.
He will now miss the game in Buenos Aires and has been replaced by new cap Jonny May.
B&I Lions coach Warren Gatland said that with several key backs undergoing treatment he felt he needed cover.
"It is prudent to make sure we have enough backline cover," Gatland said.
"Christian played well in the first Test against Argentina [last week] and is match fit."
The Lions - whose defeat of the Waratahs maintained their unbeaten record on tour so far - play the Wallabies in their first Test next Saturday.