However a further blow in Saturday's game and subsequent X-rays has revealed a fracture.
Robshaw will remain in South Africa as England continue their preparations for the Coca Cola Park Test where Northampton Saints' Dylan Hartley will lead the Red Rose.
"Chris as you would imagine is devastated," said England head coach Stuart Lancaster.
"He has led us superbly in the last seven internationals and been one of our standout performers. But the medical advice is that he should not play and we have to trust that expert opinion.
"Dylan Hartley will captain the side. He has been a key part of our leadership group and I know he will step up to the task on Saturday."
The Harlequins No8 is hugely disappointed to miss the third and final Test but is determined to remain a positive influence in camp ahead of the Springbok showdown and tomorrow's friendly with the Northern Barbarians.
"I'm absolutely gutted," added Robshaw. "I've been very proud and honoured to lead this group during the Six Nations and on this tour and it's a difficult way to end the season. I know the lads can raise themselves for tomorrow and Saturday and I will be doing everything I can to support them."