Erasmus also mentioned the possibility of fielding one of his coaches against Wales this weekend if they suffer a late injury crisis.
Former number eight Duane Vermeulen is one of the last resort options for the Test in Cardiff.
Vermeulen, 39, retired after the World Cup final in Paris two years ago with 76 Test matches under his belt.
“We kind of rolled the dice because we really only have 24 players,” said Erasmus.
“If we have any injuries before Saturday Ntuthuko Mchunu is the 24th man, and Duane Vermeulen is currently the 25th man.”
Thirteen players from the Wales squad have returned to their English and French clubs, with Steve Tandy’s side having scored half-centuries against both Argentina and New Zealand with their first-choice line-up this autumn.
“Both teams were in a similar situation in terms of player availability, but they have a balanced squad with some experienced players and a number of young players who will be desperate to make a statement,” said Erasmus.
“So, we’re expecting them to come firing and throw everything at us.”
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