The Power are smarting after last week’s shattering 12-point loss to Carlton, but having been the last team to beat Geelong at Skilled Stadium, the club is confident a four-quarter effort will topple the Cats.
"Our best form will beat them and we really have to believe in that," Williams said.
"We have to see if we can get four quarters of our best form together and, if we can, we’re pretty confident we’ll win."
Beating the premiers on their own turf is a task made even tougher by Port Adelaide’s struggle to put four consistent quarters of football together for the entire season.
"If you think of it in the sense of a ‘perfect’ game then we’ve had zero of those games this season, but the fact is that no-one else does either," Williams said.
"Even those teams at the top of the ladder find it hard to maintain their best quality football for an entire game. We’re below what they’ve been doing, but the quarters won will tell you we’ve been in the game lots and lots of times.
"But how many times have we been good enough? Four times."
Chad Cornes trained with the forwards on Friday, suggesting his troublesome knee will be tested again on Sunday.
"Chad was pretty down on what he could deliver last weekend," Williams said.
"But we’ve spoken, we’ve talked to the doctors and we fully believe he’ll be a lot better this week."
Williams forecast more than two changes to the side that lost to Carlton last week, with Nick Lower expected to replace Nathan Krakouer in the 22.
Lower will add grunt to the team, with its hardness questioned over the past month.
Williams said the Power had spent more time than usual working on winning the contested ball in preparation for Geelong.
"The amount of time that we spend on physical one-on-one and crash-and-bash training maybe isn’t always reflected in a game, but we’d like to think that the more you practise it, the better you get at it," he said.
"When you lose like that [against Carlton], everyone felt better after we trained like we did on Wednesday, which was much more that way [focused on contested ball].
"You always put a focus on something and this week it’s not inside 50m kicks, or kick-outs. It was more about winning the contested ball.
"We’re playing Geelong as well and we’re very mindful of how well they play in that area too. It’s a little bit about last week, but certainly about this week as well."
