McLaren got injured after Mitchell Johnson hit him on the arm with a short and quick delivery in the 29th over.
Though the strike appeared minor, he was admitted to hospital on Wednesday and has been ruled out of the series due to the broken arm.
This is the second time that Johnson has terrorised McLaren in six months. A Johnson thunderbolt brushed in the side of his helmet at Centurion which left the 31 year old covered in blood and bleeding from the ear. He missed the second Test.
“Ryan was taken for X-rays this afternoon after complaining of severe pain following a blow to his right forearm yesterday. The scan revealed a hairline fracture to the bone in the right forearm, which rules him out of action for the next three weeks. He will return back to South Africa on Thursday morning,” said South African team doctor, Dr Mohammed Moosaje.
Coincidentally, Johnson is the same man who caused Zimbabwean seamer Tinashe Panyangara to be sacked from the team after he sent around a video of Johnson battering England batsman to his team mates on instant messenger Whatsapp on the eve of their match against Australia.