Mitchell Johnson's numbers in South Africa: 12 wickets, 1 concussion

The significant toll of Mitchell Johnson's ferocious fast bowling against South Africa stands at 12 wickets, one concussion and plenty of bruises, and the teams are only one Test into the three-game series.

South Africa allrounder Ryan McLaren was ruled out of the second Test on Tuesday with concussion after being hit a crunching blow on the side of the helmet by a Johnson bouncer in Australia's 281-run hammering of the home team at Centurion in the series opener.

McLaren, who bled from a cut on the right side of his head after being hit on Saturday, was admitted to a Johannesburg clinic on Sunday, examined by a neurologist and concussion specialist, and kept overnight after displaying delayed symptoms.

Although the team said he sustained a "mild concussion," it was still enough to withdraw him from the second Test in Port Elizabeth starting on Thursday. McLaren did carry on playing after on-field treatment at Centurion and was out soon after being hit.

"Ryan was admitted to a Johannesburg clinic on Sunday evening suffering from suspected concussion-related symptoms including worsening headaches and nausea, which started approximately 30 hours after the blow to his head," team manager and doctor Mohammed Moosajee said. "His condition improved overnight and he was re-assessed by a neurologist as well as a leading sports physician with a special interest in concussion."

The concussion specialist who looked McLaren over also works with rugby head injuries. "It looks like he's been (rugby) scrumming for three days," South Africa captain Graeme Smith said of McLaren's bruised appearance straight after the game. "But he's alright. He's a tough boy. Those are part and parcel of what you deal with as a batsman."

McLaren will be monitored over the next four to five days, Moosajee said, before a call was made on whether he can play in the third Test in Cape Town from March 1.

Before that, South Africa have to regroup after a rare humbling at home by the rampant Australians, with left-arm quick Johnson bowling at a rapid 150 kph and almost unplayable during the first Test at SuperSport Park, where he took career-best match figures of 12-127.

Along with McLaren, some of South Africa's highly rated batsmen were left bruised by blows to the body from Johnson's short-pitched stuff and Hashim Amla was greeted first ball in the second innings by a vicious bouncer that hit him square in the grill of his helmet. "I don't know what else you want me to say," Johnson replied to a question about hitting Amla on the helmet. "It's a nice feeling from my point of view as a fast bowler."

The majority of South Africa's squad arrived in the hot and humid south coast city of Port Elizabeth on Monday to figure out a way to get back into the series as McLaren stayed behind in Johannesburg. Wicketkeeper-batsman AB de Villiers, the one South African to resist Johnson in the first Test, joined the squad on Tuesday after attending to some personal matters, a team spokeswoman said.

McLaren's absence will force the top-ranked Proteas into at least one change as they look to save their five-year unbeaten run in Test series, with allrounder Wayne Parnell and batsman Dean Elgar contenders to fill McLaren's role.

While St George's Park is normally a slower pitch to SuperSport Park, Johnson will likely still be a strong threat, and even his own teammates don't want to face him in net practice. "Unfortunately I've got no choice. I've got to face him," Australia captain and batsman Michael Clarke said.