Three days after allegations about his private life first surfaced in the newspapers, and after an assurance that his mind was fully focused on the job, Rooney proved as good as his word to launch the Three Lions to an impressive 3-1 win over Switzerland.
In firing home Glen Johnson's 10th-minute cross, Rooney was scoring for the first time in 12 England games and ending a full year without an international goal.
"I had seen he had been okay in training, now he plays an official game really well," said Capello.
"The players want to play without other things on their minds. They can focus on the game alone. He did that today.
"At the end, he was really happy."
Capello appears to have found a position that can get the maximum from the Manchester United forward.
Playing in a deeper role, behind a lone striker - first Jermain Defoe, then Darren Bent after the Tottenham man was forced off with an ankle injury that Capello claimed "was not serious" - Rooney revelled in the space, just as he had done against Bulgaria at Wembley on Friday.
"Wayne Rooney played very well," said Capello.
"(Mentally) he was okay and scoring the goal helped too.
"This position is good for him. It is easy for him to get into positions to shoot."
If Defoe had shown the same predatory instincts that brought him a hat-trick against Bulgaria, England would have been out of sight at the break.
Defoe wasted two gilt-edged chances and had another goalbound shot beaten away by Diego Benaglio.
It was not until substitute Adam Johnson nipped round Benaglio that England had some breathing space and even that did not last long as Xherdan Shaqiri scored with a thunderbolt drive.
Before that flurry of activity, Stephan Lichtsteiner had been sent off, incorrectly in Ottmar Hitzfeld's view, for a foul on James Milner, having earlier been booked for dissent.
The reduced numbers meant Switzerland were handicapped in their search for an equaliser and Bent sealed victory with his first international goal two minutes from time.
"Switzerland, on paper, were the most difficult opponents in our group so to win here is really important," said Capello.
"But the result wasn't everything. It was also about the performance of the team."
Capello was delighted with Adam Johnson's contribution, which raised more questions about why the Manchester City winger - one of six Blues on the pitch at the end of the match - was left out of his World Cup squad.
Johnson must come into contention for the third group game, against fellow unbeaten side Montenegro at Wembley on October 12, although Theo Walcott should be fit after fears the Arsenal man had broken an ankle in the build-up to Rooney's opener were quickly dispelled.
"I spoke with Theo and he told me it is not a big problem," said Capello.
"I said 'two weeks', he said less."
The overall performance was in stark contrast to England's dismal World Cup efforts and raised question marks over absent star men John Terry, Rio Ferdinand and Frank Lampard, who have not been missed in an opening to qualification that has garnered six points and seven goals.
"You know my answer," said Capello when asked about the difference in his team.
"We are really good in this period because we are fresh.
"All the players can run, their minds are free. Everything they try to do comes off."
Hitzfeld conceded Switzerland had found it hard to contain their visitors in that blistering opening period.
But, having somehow clung on, the German bemoaned Lichtsteiner's dismissal, although he admitted the full-back had been stupid to collect that first booking.
"The second yellow card was harsh because he played the ball but I am angry with the first because we know Italian referees don't like players questioning their decisions," he said.
"The player plays in Italy and knows what it is like, so that was unprofessional."