He believes his disappointing season has gotten to the point where quarterback Tony Romo and offensive coordinator Jason Garrett have lost trust in him.
Some snaps are being given to rookie Kevin Ogletree, and Williams said if he doesn't play better, he could very well lose his job.
"You know I have to get the confidence of my quarterback, because I didn't get a look after the first half," Williams said. "I didn't get a look in the second half. That's telling me that my quarterback has lost confidence in me, and so has the coordinator as far as calling plays for me.
"That's not on them. I don't blame them. I blame myself. I've got to get my crap together and try to help this team win some games in the playoffs."
The Cowboys remain supported of Williams publicly, however.
Owner/general manager Jerry Jones said he does not believe that Romo and Garrett have lost confidence in Williams.
"I don't believe that is the case at all," Jones said. "On a personal basis and on a professional basis, I have not (lost confidence in Williams). I know the kinds of plays he is capable of making and can make. I think we will see those as we go into Philadelphia and the playoffs. So I feel very good that he is on our team and out there with a chance to make plays."
"No one has lost any confidence in Roy," said Romo, who added that he appreciated that Williams wanted to improve. "Roy is going to be a huge part of this going forward. He knows that. Hopefully we're all going to have some good football ahead of us."