The England manager claimed his side, who were booed off at the end at the Green Point Stadium, were unrecognisable from the team which had won nine out of 10 matches in qualifying. And he did not rule out resigning if England did not make it through to the last 16.
When asked if he would go if they did not get the win they need to definitely progress from Group C against Slovenia next Wednesday, he said: "It is too early to speak about this. We have to wait."
Capello, however, did give an honest appraisal of one of England's worst-ever FIFA World Cup performances, in which Wayne Rooney, who has not scored for his country in more than 11 hours of football, was frustrated and out of sorts. Capello, who saw his side draw 1-1 with the United States in their first match, said: "We did not play a good game. We missed a lot of balls when we had to control. We missed a lot of passes and when we arrived at the box we tended to shoot at the goalkeeper. We missed everything. In this game I did not see the spirit of the team."
When asked what was wrong with Rooney specifically he said: "I don't know. I don't like to speak about the performance of one player. I prefer to speak about the performance of the team. Rooney didn't play like Rooney, but he is not the problem. It is the pressure of the World Cup. These players are training very well at a fast speed. But these two games they were not the same."
Capello also admitted they were "lucky" to still have a chance of getting to the last 16 after the USA drew 2-2 against Slovenia. "We have to be focused for the next game," he said. "We have a big chance to go through after the draw of the United States.
"I hope on Wednesday to see the England team. This is not the England that I know. It is not the players in training. When I started as England manager, I saw the same things when we played at Wembley. I hope for the next game that we forget this performance and forget to play with fear and without confidence.
"It is incredible the mistakes of the players, when they do not control the ball, the easy passes we missed. Everything. This is incredible for the level of the England players. It is the pressure. It is so big that the performance of the players is not as good as I know."
Capello also dismissed the notion, posed by former England boss Graham Taylor, that there might be problems in the training camp. Capello said: "This is incredible. I think we have the best training camp. We are training well together always. The problem is not the training camp. The problem is the players who were so good as a team are not so good as a team at this moment."
The manager, who turned 64 today, is hoping one big performance could yet reignite his squad. He added: "I hope that after playing a big performance the minds of the players will be free and we can play like the England that I know. This is very important."
But while Rooney claimed the fans should not have booed the team as he left the field, Capello backed the supporters. He said: "I think always the fans can decide to do what they prefer. I respect the fans. They always follow us. They always help us."