"It's something that I have been thinking about for a long while," said Supple "It's obviously a big decision, but I feel that playing professional football is not something I want to continue doing as a career.
"There is no one reason why I have made my decision. There are a number of factors, but deep down my heart is not in the game any more. I'm not going to go into work every day trying to convince myself that it is, so it's the right time for me to walk away."
Conspiracy theorists immediately looked in Keane's direction for an explanation, but Supple quickly scotched any suggestions that the new management regime at Portman Road had impacted on his decision in any way.
"I want to thank the manager for the support he has given me," said Supple. "He was a bit shocked when I told him, and I expected that, but he understood my reasons. He's been first class.
"People probably think I'm crazy, but I'm not going to stay in the game for anyone else. I'm making this decision for myself. I've worked with some great people in my time at Ipswich Town and had some great times at the club.
"It's a fantastic football club and I'll continue to follow Ipswich's fortunes. The supporters have been brilliant as well and always backed me and I want to thank them for that wonderful support.
"This is the right decision for me now. I'm going back to Ireland to spend time with my family and look at my options, but they won't be in football."
Ipswich Town Chief Executive Simon Clegg said: "On behalf of the club, I would like to put on record our thanks to Shane for his commitment to Ipswich Town both on and off the pitch in his six years at Portman Road.
"It's obviously disappointing news for us, but we respect Shane's reasons for wanting a career change and we wish him every success for the future."