Former Test referee Alain Rolland has called on World Rugby to investigate Rassie Eramsus being employed as the Springboks' "water boy".
Erasmus' official role is SA Rugby director of rugby, but he's been on the sidelines of late carrying tactical messages during the warm-up games for the British & Irish Lions series.
Lions coach Warren Gatland has already poked fun at Erasmus' role, saying if he wanted to be a "water boy", he should at least be carrying water onto the field.
"I didn't quite understand what his role was. You don’t run onto the pitch, carrying messages without the water. My advice is next time, he must make sure he is carrying water when he does that," Gatland quipped after his side's 17-13 loss to South Afriva 'A' at Cape Town Stadium earlier this month.
However, in an interview with the Daily Mail, Irishman Rolland, who took charge of the 2007 World Cup final in which South Africa beat England 15-6, said that Erasmus was technically bending World Rugby's laws.
"Rassie Erasmus shouldn't be allowed to play the role of water carrier on Saturday," Rolland said. "Head coaches are not allowed in the technical zone. He is head coach in everything but name.
"It doesn't sit comfortably with me. I've got no doubt that it will get looked at by World Rugby. I’ve got no doubt that it's been raised this week and will get looked at by World Rugby.
"It may be very difficult to stop because technically South Africa are not breaking the protocol. If South Africa are able to prove that he's not the head coach, there may not be an awful lot of action that can be taken in such a short period of time. It's hard to change these things on the hoof.
"There's normally a protocol to change a protocol. Even if they want to do something about it, they may have to wait until November."
Erasmus coached the Springboks to World Cup glory in Japan in 2019, but has since taken a back seat with Jacques Nienaber stepping in as head coach.
Saturday's first Test at Cape Town Stadium kicks off at 18:00.
15 Willie Le Roux, 14 Cheslin Kolbe, 13 Lukhanyo Am, 12 Damian de Allende, 11 Makazole Mapimpi, 10 Handre Pollard, 9 Faf de Klerk, 8 Kwagga Smith, 7 Pieter-Steph du Toit, 6 Siya Kolisi (captain), 5 Franco Mostert, 4 Eben Etzebeth, 3 Trevor Nyakane, 2 Bongi Mbonambi, 1 Ox Nche
Substitutes: 16 Malcolm Marx, 17 Steven Kitshoff, 18 Frans Malherbe, 19 Lood de Jager, 20 Rynhardt Elstadt, 21 Herschel Jantjies, 22 Elton Jantjies, 23 Damian Willemse
British and Irish Lions
15 Stuart Hogg (Scotland), 14 Anthony Watson (England), 13 Elliot Daly (England), 12 Robbie Henshaw (Ireland), 11 Duhan van der Merwe (Scotland), 10 Dan Biggar (Wales), 9 Ali Price (Scotland), 8 Jack Conan (Ireland), 7 Tom Curry (England), 6 Courtney Lawes (England), 5 Alun Wyn Jones (captain, Wales), 4 Maro Itoje (England), 3 Tadhg Furlong (Ireland), 2 Luke Cowan-Dickie (England), 1 Wyn Jones (Wales)
Substitutes: 16 Ken Owens (Wales), 17 Rory Sutherland (Scotland), 18 Kyle Sinckler (England), 19 Tadhg Beirne (Ireland), 20 Hamish Watson (Scotland), 21 Conor Murray (Ireland), 22 Owen Farrell (England), 23 Liam Williams (Wales)