Bagshot - England coach Stuart Lancaster has said on Monday that he was "optimistic" that forwards Courtney Lawes and Dylan Hartley will pass concussion tests in time to face the Springboks at Twickenham on Saturday.
The Northampton duo both suffered blows to the head during the course of England's 24-21 defeat by world champions New Zealand in their opening November international at Twickenham last weekend.
Second row Lawes left the field in the first quarter while hooker Hartley lasted until the final 10 minutes.
Both players will be assessed under standard concussion protocols but Lancaster was confident they would be fit by the time he announced his side to play the Springboks on Thursday.
"Courtney is symptom-free so hopefully he will be OK," Lancaster said. "Dylan has also got bit of a head knock and is in the same situation.
"They need to train on Thursday to be ready. They will do a cog (cognitive) test on Thursday morning which they have to pass to train.
"We will have provisions in place should they fail that, but we are optimistic they will be available."
England's loss on Saturday was their fifth successive defeat by the All Blacks and came after they led 14-11 at half-time.
But, as has happened before against New Zealand, a lack of game management and poor kicking cost England dear, albeit they were missing several players due to injury.
"The review was honest and pretty straight. We didn't gloss over anything and we know we have got to improve against South Africa," Lancaster said.
"We were up at half-time and deserved to be in that position, but obviously we were pretty hard on ourselves in not taking the opportunities we should have done.
"We know that at this level if you don't take those opportunities they can sometimes come back and hurt you. Clearly that was the case in the second half."
Lancaster added: "New Zealand played well in the second half and we didn't play as well. Our kicking game wasn't good enough and put us under some pressure.
"New Zealand managed that period well when they turned the ball over and that period that led to their try by Richie McCaw was disappointing."
South Africa are the only major rugby nation 2015 World Cup hosts England have yet to beat since Lancaster became their coach two years ago.
England's record against the Springboks during that time stands at three defeats and a draw in four Tests.
South Africa have arrived in London for their latest clash against the Red Rose brigade on the back of a shock 29-15 defeat by Ireland on Saturday and Lancaster is braced for a 'boklash' at Twickenham.
"There will be a reaction from South Africa this weekend, I don't doubt it. Ireland deserved the win," Lancaster said.