O'Connor's contract ran out this summer, but due to Football League regulations - Stoke can still demand a fee for the 23 year old midfielder.
James, despite being happy at joining a new club, was sad to say goodbye.
"The main reason I am leaving is because I'm out of contract and just feel it's the right time to move on.
"I've always had a great relationship with the fans, and now I just hope they will understand my reasons for going.
"Hopefully, they will remember me as a player who always worked his butt off for the club."