The 34-year-old, who is England's sixth-highest wicket-taker with 255 in Tests, said he had expected the captain, Alastair Cook, to drop him for the third Test, such was his poor form going into the match, but having been selected, Swann soon realised in Perth that the game was up.
"It was very hard telling Cooky in the first instance, because he's such a good mate. He spoke to me before the Perth game. He called me downstairs, and I fully expected to be dropped after the way I played in the first two games.
"And I'd come to peace with that, I was fine with it. But he said, 'I need to know you've still got the fire in there, and you can still go out there and really fight for me', and I said, 'Of course I have. I've got the fight, whether I've got the skill any more is another thing, but I'll fight my nuts off for you.'
"After the Perth game, I proved to myself during that game when Shane Watson was hitting it at will for six and I was powerless to stop it, how could I possibly carry on when I know that I can't do the job I'm paid to do any more? Can't put enough spin on the ball to have enough control to worry good batsmen any more.
"So people saying, 'You should definitely have carried on playing', I just don't understand that. If someone has come to the realisation that they're not good enough, why would you want them to keep playing?"
-THE INDEPENDENT