The ex England international has also previously stated that he would be willing to drop down a couple of divisions to extend his playing career.
"He has been really influential. He has been a great captain and a great player since he joined us eight years ago and will be missed," Moyes told Yahoo Sports.
"He has been someone that I can rely on both on and off the pitch.
"I have got no doubt that he will go on to work in football and he is someone who we will miss.
"It will be a hard position to fill because the way he has captained the team has been excellent over the years."