Hodgson claimed he had overlooked Ferdinand because it would have been wrong to have him in his European Championship squad and not in the starting XI.
The new England manager told ITV: "Rio Ferdinand for me is not a player that you call up as a substitute, or to cover for the players that you have.
"We turned to Martin Kelly because I knew he was going to be someone who would be very useful to us.
"He's very happy to be here knowing that his chances of playing a big part in the tournament are quite small.
"You don't turn to people like Rio Ferdinand for that."