If he wanted to quit football, why would he put in a transfer request?
Probably something in his contract about buying it out at 'x' amount if he hasn't been sold while transfer listed after a certain period of time. God knows what agents get up to these days. I doubt he would quit football altogether he doesn't seem burntout while he is playing if he was so sick of it he could just bugger off or say he's injured so can't play or what ever.