Luke O'Nien penned a tribute on Twitter to the Chairboys after completing his transfer to Sunderland.
He wrote: "My time has come for me to move on from WWFC after one hell of a three year journey!
"I would like to thank every person connected to the club that has made my time so special. You have all helped me to develop both as a player and a person and I can't express my gratitude enough.
"Receiving all the messages of love and support on Twitter has been overwhelming and has filled me with great joy. I have so much respect for everyone affiliated with Wycombe Wanderers and will remain a fan of the club forever!
"I wish you all the best for the upcoming season and will see you all soon."