He just didn't do it.
On third-and-10 from the Dallas 46 with no timeouts and 12 seconds left, Williams caught a pass in the right flat. Instead of sprinting out of bounds at around the New York 47, Williams inexplicably turned upfield and gained 5 more yards.
But time expired as the Cowboys were lining up to spike the ball and stop the clock.
"I don't know, I was just doing my best to put the team in a position to kick a field goal," a solemn Williams said after the game. "Obviously, I should've just followed the rules and got out of bounds.
"The whole purpose of me cutting it in was to go right back to the sideline to pick up more yardage. Breaking the huddle it was already third-and-13 [sic]. In my mind, I was trying to make the first down and dive out of bounds -- it just didn't go as planned. I was clearly aware of the time. It was something I was just thinking of, and it was a bang-bang moment. Now that I have a time to sit back and think about it, I should've just went out of bounds."
As the Giants streamed on the field to celebrate their come-from-behind win, Williams fell to his knees. His head dropped and he stared at the ground for several seconds. Dez Bryant whispered into Williams' ear, and coach Jason Garrett patted the receiver on the shoulder as he walked past him toward midfield to greet New York coach Ben McAdoo.
"What he needed to do there was simply run out of bounds," Garrett said. "It's a well-practiced situation. We've been in that situation a lot and his instinct took him inside. Obviously with no timeouts and 12 seconds to go, he needs to catch that ball and immediately get out of bounds and we'd asses the situation from there as to whether or not we kick it from there or try to get a little closer."
Williams finished with three receptions for 34 yards and one horrendous decision.
"The coaches are still with me. I should've just followed procedure and went out of bounds," Williams said. "The players and coaches are still behind me 110 percent. It's just something where I should've followed the rules.
"It's always good whenever you have a great group of guys who will come to your aid and pick you up when you're down. They talked to me and kept me calm. It's still a poor decision for me, but it's one of those things that happened in a bang-bang moment. Looking back, I'll never do that again."
Linebacker Sean Lee said Williams has made big plays for the Cowboys in the past, and he'll make them in the future. Bryant said he told Williams to keep his head up.
The Cowboys didn't lose because of that one play. They lost because they averaged 3.4 on 30 carries, Cole Beasley dropped a pass at the Giants' 4 that he probably would've scored on, Bryant had an apparent touchdown overturned by replay and the defense couldn't make a play when it mattered in the fourth quarter.
Fans, as you would expect, are all over social media blaming Williams for the loss.
"It doesn't bother me. I'm used to people blaming me anyway. It's not something new," Williams said. "I know what type of guy I am. I know how hard I work, and hearing different people talk about me is not going to bother me, because at the end of the day I'm still here doing my job and I'm trying my best to put my team in the best position to win.
"So I can't keep paying attention to what people say because they're going to talk about me regardless. I just focus on what my coaches and teammates say. The rest of the people don't have anything to say to me."