He had his best game of the season Sunday against the Packers with five catches for 105 yards and a touchdown, but all anybody remembers are the two mistakes he made that hampered the Cowboys' ability to win the game.
Williams had a fumble following a 42-yard catch that killed a scoring opportunity deep in Packers territory.
He also dropped a pass at the Packers 35-yard line on a drive that could have led to points.
At least a field goal on either possession could have changed the game.
"That could have been the big play that got us out of kind of the doldrums there," coach Wade Phillips said of the fumble.
After making just 14 catches in his first six games, Williams has 10 catches for 180 yards in the last two. That has led Phillips to emphasize the positives.
"It looked like the timing and stuff, the touchdown, even the touchdown at the end, the slant pass he had, the other slant passes he had over the middle, we're getting a feel for what he can do," Phillips said.
"And you can smoke it out to him on a running play and he's going to run over the defensive back, so we're starting to get a feel for his physicality."
TUESDAY LEFTOVERS: Running back Marion Barber saw his time limited against the Packers because of problems with a fractured left thumb that was causing him trouble on pass protection at Green Bay.
Barber had four carries in the first half for 26 yards, but he carried it just one time for minus-1 yard in the second half. The Cowboys went with Tashard Choice because he could handle the blitz pickups.
"We use Marion because he's such a dominant blocker," coach Wade Phillips said, "but he was having problems so we took him out."
* Running back Felix Jones remains a conundrum for the Cowboys. They went to get the ball in his hands as much as possible because he is a home-run threat, but they have to limit his time on the field because he is injury-prone and because he still has trouble in blitz protection.
"He's just not as adept at it yet," Phillips said of Jones' blocking. "He missed a whole year of that (last season), where (Tashard) Choice didn't. Choice played. He knows his assignments well and does a good job of blocking."