The former Cardiff City full back has been struggling with a knee injury. Delaney, still just 31, made 193 appearance for Aston Villa, also winning 36 caps for Wales.
His last cap came a year ago against the Czech Republic.
His Villa boss Martin O'Neil said today
"Mark has tried absolutely everything to get back to fitness.
"He's been dedicated, coming in here every single day and everything he's been asked to do, he's done.
"He's gone to the very best people and he's tried everything. I'm sure he has a future in the game and I wish him all the best in whatever he does."