The Reds won 1-0 to secure consecutive clean sheets for the first time since September and the 19-year-old believes the victory, courtesy of Juan Mata’s 67th-minute chip, was built from the back.
“As long as we don't concede, we know we're going to score,” Williams told MUTV after the final whistle.
“If we do our job at the back and the full team puts the shift in, I'm sure we'll get the win like we did.”
United finally managed to beat Nuno Espirito Santo’s side at the sixth attempt since their promotion in 2018, after three draws and two defeats in five previous meetings.