Cape Town - Springbok flyhalf Handre Pollard is in doubt for South Africa's Rugby Championship Test against Argentina in Durban on Saturday.
Kick-off is at 17:05.
Pollard is struggling to overcome a knock to the head he suffered in the 27-20 loss to New Zealand at Ellis Park in Johannesburg on July 25.
Pollard was temporarily replaced in that match by Pat Lambie, but did return later to resume his No 10 duties.
The fact that Pollard is some nine days later still suffering the effects of the knock casts serious doubt on the effectiveness of off-field concussion protocols conducted during matches.
Springbok doctor Craig Roberts explained on Monday that although Pollard passed concussion tests conducted on him both during and immediately after the match, he failed a mandatory cognitive test carried out two days after the game.
“Handre passed the head injury assessment during the game and immediately after, but then two days later there were signs of what we called delayed concussion. So we will only know later in the week, after further tests are carried out, whether he will be available for selection,” said Roberts.
Should Pollard be sidelined for the 'dead' Rugby Championship Test at Kings Park, home-town favourite Lambie and France-based pivot Morne Steyn are the most likely candidates to fill the void.
Coach Heyneke Meyer may well elect to give Lambie or Steyn a run as Pollard has played every Test this year and he'll want to ensure all his options in the flyhalf position get game-time prior to the Rugby World Cup.
Meanwhile, other players with injury concerns - Vincent Koch, Warren Whiteley, Trevor Nyakane and Marcell Coetzee - all have an outside chance of playing this weekend.
Players likely to return from injury include Pieter-Steph du Toit, Jean de Villiers, Fourie du Preez, Jan Serfontein, Stephen Kitshoff and Willem Alberts.
Victor Matfield, JP Pietersen, Jannie du Plessis, Francois Louw, Duane Vermeulen, Coenie Oosthuizen and Frans Steyn were all watching from the stands on Monday as the Boks started their build-up and won't feature on Saturday.
After Saturday's match, the Pumas and Springboks will board a flight to Buenos Aires for the final pre-World Cup warm-up at the Estadio Jose Amalfitani Stadium on Saturday, August 15.
Kick-off is at 21:40 SA time.