Some critics questioned the players' motivation.
But injured England captain Ferdinand told The Sun: "I don't think that's ever a question when you put on an England shirt."
However, he agreed the squad - aided by the injured David Beckham - SHOULD have done better. He continued: "I understand fans' anger.
"People pay good money to go and watch football. If people are angry you can't knock that. They pay their hard-earned money to watch us all over the world so that's part and parcel of it.
"When you look at the names on our team-sheet, you'd have to say that not getting to the latter stages of the tournament that you've under-achieved.
"With the players that we have got, you have got to be disappointed.
"We went into this tournament feeling 100 per cent capable of winning it. So to go out at this stage, regardless of who you're playing, is disappointing.
"To look at it as an under-achievement, given the players we've got to choose from, is a fair point."