Matthew Stafford's wife Kelly penned a "Thank You" note to the city of Detroit amid reports the Lions QB has mutually agreed with the franchise to continue his career elsewhere.

Matt has played every down of his pro career with Detroit since he was drafted out of Georgia with the 1st overall pick in the 2009 NFL Draft.

Now, ESPN says Detroit -- and Stafford -- have agreed to a conscious uncoupling ... so Detroit can draft new franchise QB and 32-year-old Matt can try his luck in another city.

Enter Kelly ... who is bracing for the move.

"Thank you," Kelly said in a note to the people of Detroit ... "This place, our home, the people ... it’s hard to find the words to explain what this place means to me."

"Random tears come very often when I think about not being here."

"This place supported me during the toughest time of my life and during the happiest times and I want to thank y’all in the right way."

Kelly and Matt have 4 kids together -- all born during Matt's time with the Lions. Also, Kelly underwent brain surgery for a tumor in 2019.

So, what's next for the Stafford's?

"Whenever I figure out what the future holds, you’ll be hearing from me again with a thank you that hopefully shows how much gratitude and love I have for this place," Kelly said.

"But until then we are going to enjoy our time left in Michigan to the fullest because there really is no other place like it."

There are rumblings Matt could end up in San Francisco to play for the 49ers -- but it's all talk at this point.