The Manchester City is currently recovering from the problem and is facing a race against time to prove his fitness ahead of next month's World Cup.
Capello plans to name his final 23 on Tuesday and is convinced Barry will be a part of it even if he is set to miss the opening group stage match against the USA.
"The tests and scans of two days ago say that his ankle is doing well, much better than we had thought," Capello said.
"Most importantly, it looks as if the recovery times will be much shorter.
"We will wait until the end of the week and then we will decide if Barry will or won't play in the World Cup but we are very hopeful."