The Scottish team management are concerned a viral infection may cripple their team ahead of the second Test against the Springboks on Saturday.
On the plus side, the slew of injury worries eased with Donnie Macfadyen and Hugo Southwell returning to training yesterday.
Captain Jason White did work with the team physio and was confident the recurrence of his knee knock would not keep him out, The Scotsman newspaper reported.
Winger Sean Lamont – whose clash with Jean de Villiers caused the midfielder several cracked ribs – is unlikely to be risked, with try-scorer Simon Webster set to fill in.
The viral concern is currently only with back-rower John Beattie, who was confined to his room, but Hadden admitted that it might only be the “tip of the iceberg” as other players had felt unwell.
Scotland remained in Durban to train and will only fly into Port Elizabeth on Friday morning.