Rooney's contribution was one of the most disappointing aspects of England's goalless draw with Algeria in Cape Town and his performance in the opening game against the USA was equally as poor.
Not only was the 24-year-old unable to break a scoring drought in tournament football that stretches back six games to a group encounter with Croatia at Euro 2004, he made a succession of unforced errors and after the final whistle complained about the behaviour of England supporters - many of whom booed their team at the final whistle.
Inevitably questions have been raised about Rooney's fitness given the amount of time he spent on the sidelines after suffering an ankle injury in the Champions League quarter-final first-leg defeat to Bayern Munich in March.
But Capello has backed up Rooney's own claim that he is fine, and instead indicated there may be mental issues at play.
"He is completely fit," said Capello. "He has trained and he has been on the pitch for as long as any other player. He is perfect.
"The problem is in the mind. I know this.
"I was a player. I remember these moments. In the mind you are okay. Then you get to the pitch."
It is a similar accusation Capello has made against his team as a whole.
The problem was one he inherited and goes to the very heart of his attempt to turn the Three Lions into winners.
A change of personnel is now being called for. But the prospect of England heading into a must-win contest with Slovenia in Port Elizabeth on Wednesday without their talisman, the player who remains most likely to get them a goal, is unthinkable. And it doesn't seem to have crossed Capello's mind.
"Wayne is a good player," said Capello.
"He is always dangerous for the opposition because of his movement and general play.
"I know he gave the ball away a lot yesterday and some of his passes were not good but he is still an important player."
Capello seems determined not to discuss his future, even though it is widely anticipated the Italian could not survive a failure to make it out of the group in such an abject manner.
If England were to go out on Wednesday, many expect the Italian to walk away from the long-term deal he signed only three weeks previously. It would certainly be hard for him to continue in the position.
No plausible explanation has been put forward for why Joe Cole, one of England's most creative players, has been left kicking his heels on the bench when Shaun Wright-Phillips has been brought on in both games so far with minimal effect.
Instead, Capello is concentrating on ridding himself of the faults that are costing England so badly, except he is not entirely sure how.
"This is a good question," said Capello when asked what he could do to improve the performance of his team.
"I have spoken a lot with the players. We have trained all the time and we have practised everything.
"But when we have played we have lacked the same pace.
"The fear of the World Cup is in the mind of the players. It is incredible.
"The performance in training is good. But the players on the pitch are not the same ones that I know."
England's bad performances have come as a huge shock to thousands of travelling supporters in South Africa as well as millions back home.
And, after easing through a tough qualifying group with nine wins from 10 games - losing only to Ukraine after Robert Green had been sent off - the collapse has left Capello nonplussed as well.
"I am surprised," he said. "I can remember exactly what happened in the first game we played against Switzerland at Wembley after I took over.
"I also remember after we beat Croatia away we started to play differently. Now I hope it will be the same.
"We have to play like we train. But the problem is not only when we win the ball. We have to win it back quickly.
"We have to press the opponents to win back the ball. I want to see that spirit."