The New Zealand official was jeered off, and criticised afterwards by France captain Antoine Dupont, for his officiating on Sunday (local time), as South Africa narrowly edged the hosts 29-28 in the quarterfinal with several marginal decisions going the Springboks' way.
World Rugby raised eyebrows earlier on Tuesday by naming O’Keeffe to handle Saturday’s semifinal at Stade de France in Paris, but Erasmus said it was not unprecedented to have the same referee three times in a World Cup.
The 34-year-old O’Keeffe was also in charge when the Boks lost to Ireland in their pool game.
“We also had Jerome Garces as our referee for the opening game of the last World Cup, and then the semi-final and final as well,” Erasmus told a news conference near their team base on the outskirts of Paris on Tuesday.
O’Keeffe has yet to officiate England at this tournament, but Erasmus felt this would offer neither side any favours.
"I guess it's a bit of an unknown, either positive or negative. It will be best for the team that stays within the laws and hopefully doesn’t have rugby accidents, causing cards, although I think that's one thing that Ben has really done well, and I think (England coach Steve) Borthwick will be as pleased if he referees the game like that again.”
Erasmus said England posed a massive “pothole or roadblock” in South Africa’s way as they hope to defend their title in the final on October 28.
“They are unbeaten in the tournament and have stuck to their guns and kept believing in what they were doing under Borthwick and you can see it's paying off, they are a team full of belief."
But amid the praise, he could not resist reminding England of recent results.
“They will be definitely hurting not only from last year when we beat them but also the 2019 World Cup final,” added Erasmus, who said South Africa’s own selection process would again be delayed until Thursday as they pondered several options and also waited to see what team England pick for Saturday’s clash at the Stade de France.
“It won’t be a 7-1 split on the bench,” he added of the Springbok’s decision in two recent tests to put seven forwards and only one back among the replacements.
“With two fit flyhalfs now, we are probably looking at a 6-2 split,” he told reporters.
Australian Angus Gardner will referee the other semifinal between Argentina and the All Blacks, also in Paris, on Friday night (local time).