The Manchester City ace is yet to play for England, but was named in Capello's preliminary squad for the World Cup finals.
Johnson provides natural width on the left side of England's midfield and looks a good bet to make the plane to South Africa.
Capello has now hailed Johnson's quality following his impressive six-month spell with City and believes his improvement means he will be included.
"Johnson is one player who is really good," said Capello.
"He has improved a lot, he is a really, really good player.
"I selected him because I think he can stay with us."
Meanwhile, Capello has confirmed Joe Hart will get 45 minutes under his belt in Monday's international friendly against Mexico.
Although Hart is only 23 with just one cap to his name Capello insists he has confidence in the keeper, just as he does with David James and Robert Green.
"He will play 45 minutes against Mexico," he continued. "I've confidence in him, just like the other two goalkeepers."