Williams was encouraged after "the Swansea way" held Napoli at bay in the first leg of their Europa League last-32 tie.
He told ITV1: "We're really pleased with the way we played, it tells you a lot that we're disappointed with 0-0.
"The message was to get on the front foot and play the Swansea way and we had a lot of chances, the performance as a whole was brilliant."
Williams said: "It's going to be a tough game, we're under no illusions going out there but we'll take a lot of heart from tonight.
"It will be a difficult game playing away but we'll get on the front foot again and see what we can do."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball