Williams believes Swansea will be helped by tonight's match ahead of the visit of David Moyes' side.
"We knew they'd come out at home and make it more difficult for us. We're pleased to not concede a goal again, that's the main thing," he said.
"We knew it would be tougher playing away. It's our first game away in Europe. It stands us in good stead for the United game next week.
"There's no tougher test than Manchester United on the first day so we'll see where we are then and a few games into the season."
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