"We started not so well against Andorra in our last match," added Capello.
"We didn't score before half-time but step by step we have moved on and improved."
England are 10 points clear in Group Six and on the cusp of securing qualification for next season's finals in South Africa.
Capello's team, who play a friendly against Holland in Amsterdam on 12 August, are effectively one victory away from securing their passage.
As things stand, England still need four points from their remaining three games to be absolutely certain of qualification because Belarus could still get to 24 points as they have five games remaining.
However, Belarus play Croatia home and away in August and early September and unless they take maximum points from those games, victory for England in their next game against Croatia at home on 9 September will secure qualification.
Capello said he could not have been more pleased with his players' performance after the 6-0 thrashing of Andorra at Wembley.
"When you play a team that is not strong you must start quickly, press and win back the ball and we did that," stated the Italian.
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Wayne Rooney and Jermain Defoe scored two goals apiece and Frank Lampard and Peter Crouch also netted as England moved 10 points clear at the top of Group Six.
Capello also reserved praise for the 57,897 fans who had made it to Wembley to support the team, despite chaos in London caused by a Tube strike.
"Sometimes it is worse in Italy when they strike," he commented. "I think when someone decides to strike it is to create problems but I am very happy about the people who came here. They enjoyed the game.
"I am very happy for the fans, very happy for the people that stayed here. I am happy today."
Midfielder Lampard, who coolly slotted away England's second goal, said the ease of the victory spoke volumes for the improvement in confidence in the squad.
"It was not as easy as it looked, that game, they just sat back," said the Chelsea star.
"But we've found ourselves as a group. We always knew we had the individuals but we weren't working as a team. You can see the results on the pitch."
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