Ferdinand has been ruled out of the World Cup qualifier against Kazakhstan.
His calf injury, a complaint he was understood to be carrying before Manchester United's Champions League final, means he will miss the trip to Almaty but could return for the clash against Andorra next week after the problem is assessed.
With Phil Jagielka sidelined, England boss Fabio Capello turned to Cahill after the 23-year-old's impressive season with Bolton.
"I was at home and I got a phone call from the FA (Football Association) saying that they wanted me in the squad," Cahill said on his club's official website.
"I've had to get a few tools together - the boots and the shin pads - and now I am really looking forward to the opportunity.
"I've had a good season and I've worked really hard. I've been in the provisional squad twice before and then this third time I was included once again, so I'm obviously delighted to get the call."