By SABC Sport
30th September 2023
The number eight joined the Springboks' brains trust during the contest with Andy Farrell's men in Paris last Saturday.
According to Nienaber, Vermeulen is taking the "Francois Louw role" at this World Cup, where he is not necessarily a guaranteed starter but can provide expertise in other areas.
"I can't say if he's preparing for the future. It's not the first time that we have had a player in the box," the Bok head coach said.
"It's good for us as coaches to sometimes have a player [there], because they give us a different perspective of how our communication is within the team.
"They get a sense of the sometimes frustration that coaches are under in a coaches' box. That grows them as a player.
"Our coaches' meeting starts at seven in the morning - any player can join that.
"Let's say it gets to something sensitive like team selection, we will excuse them from the meeting and have the internal discussion, but they are more than willing - from 2018 - to sit in coaches' meeting as much as they want.
"Duane's role; if you look back to 2019, the best way to describe it is a Francois Louw role. He's a guy that can start, that can play a Test match for you, but he's also a guy that's got a lot of experience and he adds his wealth of knowledge into the group.
"Not saying that he can't start. Look at Francois Louw, the contribution he made in that semi-final for us, to get a penalty in the 76th minute.
"Big moments, big roles, been there before - he's [Vermeulen's] probably in that mould, but if there's an injury and he has to start and play the whole game, he's more than fit and good enough to do that."
South Africa are hoping to move a step closer to the quarter-finals when they take on Tonga in their final World Cup pool match on Sunday.
Looking ahead to the match against Tonga, Nienaber said it was vital to improve a few areas of their game to book a quarter-final spot and attempt to defend their title.
"We obviously have goals if you take the results out of the way," said Nienaber.
"Firstly, we need a win, then a bonus point and a good points difference, and then there are things that we need to rectify which we didn't get right against Ireland. We need to get our foundations right to get to the quarter-final and onward otherwise we won't make it through."