The Swans face the prospect of six extra matches in the Europa League if they can make it through to the group stages, and Williams has insisted that their efforts in pre-season training are more important than in previous years.
The 28-year-old told the club's official website: "Any pre-season is important, but maybe this year it is even more important that everything is perfect.
"We will be playing in the Europa League and if we can make it through to the group stages, then there will be a lot more games on the fixture list.
"Even though we have improved every season, I think this year will be the hardest we will have faced in the top flight so far."
The Liberty Stadium outfit play their first friendly against Dutch side FC Gravenzande on Saturday.