South Africa coach Jake White felt his side gifted victory to England after the visitors surrendered an 18-6 lead in the second half at Twickenham.
White's own position will come under further scrutiny
"We probably lost it more than we were beaten and that hurts a lot," he said.
"I can only put that down to the number of inexperienced players. I don't think they could believe we were 12 points up," said White.
"If you get opportunities and don't finish them it tends to come back to haunt you."
Defeat piled more pressure on White, who was already facing calls for his dismissal back in South Africa after last week's defeat by Ireland.
"This was always going to be a tough tour, always going to be a chance to blood some youngsters and always going to be tough to beat England at Twickenham," he added.
"We have come here with some good teams and lost at Twickenham. We have come before and not played as well as we played today.
We will come back with a bigger fight next week
"Credit to England. They showed a lot of character and we showed a lot of inexperience at vital times. But we can take a lot out of this Test."
White said he replaced impressive fly-half Butch James, who had just landed a penalty to make it 21-13 after 57 minutes, because he had hurt his knee.
Springboks captain John Smit is confident his men will return for the re-match next Saturday a more ruthless outfit.
"The changing room was a disgusting place to be," he said.
"What we will learn from today is how to close off a Test match and we will come back with a bigger fight next week."