Rooney appears to be over the ankle problem which two weeks ago made the Manchester United striker a doubt for the Wembley clash.
But just as importantly Capello feels Rooney is in the right frame of mind after the recent allegations about his private life.
Capello said: "I spoke with Sir Alex (Ferguson) who told me, when I decided the squad, that Rooney would be fit because the ankle problem was not so big.
"I spoke with Rooney about the situation, his situation. I monitored him during the training and he trained perfectly, really well.
"I think it's important to monitor the players in training. You can understand a lot of things from that.
"He's focused on the game. He's happy. He's smiling a lot.
"He's in a good moment, better than he was when we played against Switzerland."
Capello is set to start with inexperienced wingers Adam Johnson and Ashley Young and knows the onus is on the duo to deliver good service for Rooney and Peter Crouch to capitalise on.
He said: "Some players, the wingers, will be very important now. They have to cross the ball.
"It will be really important, both of them. They play in a position on the pitch that is important.
"They have to try to dribble, to attack the space.
"People say they are inexperienced players but the confidence of Adam is good. He's played three or four games (for England).
"Ashley Young has also played very well in a couple of games and done well in a more central role for Aston Villa."
Capello is happy with the state of the Wembley pitch which was much criticised last season.
He said: "The pitch is really good. The people who work on the pitch have done very, very well.
"There can be no excuses with the pitch. They've surprised me with the problems they've had, but they've found solutions."
Capello will come face to face with one of his former players in Montenegro FA president Dejan Savicevic.
The Italian signed Savicevic for £9.4million from Red Star Belgrade when in charge of AC Milan in 1992 but the pair were often at loggerheads.
Savicevic eventually returned to Red Star six years later after winning three Serie A titles and the Champions League.
But Capello insists the pair are now good friends.
He said: "Dejan is a really good friend of mine. Really. It's not a joke. We phone sometimes and we met him in Austria, in Poland, and in Switzerland.
"We had some problems when he was at Milan at first, but he ended up understanding my style and was a really big player for us at Milan.
"He was one of the most talented players I had. I decided to substitute him a lot of times because, when I arrived (at Milan), he played the Yugoslavian style.
"He was the star and the others had to run for him. In the end, he understood he had to run too!
"I'm disappointed because he learned a lot and Montenegro's style is based on him, remembering a lot of the stuff I told him. He's a nice guy."