The Cats only outscored Port by nine points in the final three quarters, but a 39-point quarter-time lead meant the damage had already been done.
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Like the Power, Geelong entered last Saturday's clash having lost six of their first eight opening quarters.
Coach Chris Scott said the Cats had entered the match with a strong defensive mindset from the beginning to ensure they didn't get left behind again.
Westhoff said his side needed to do the same.
"To get seven goals to zero kicked [against you] is not great and probably comes down to our defensive stuff and just our method and how we can change that to stem the flow of goals," Westhoff said.
"It's kind of like soccer where they kick a goal in the first couple of minutes and it's pretty much game over ... we just need the mentality where, 'If I'm not getting a touch, my opponent can't get a touch either'.
"We've spoken about it at length in the review. We just need to go into games thinking, 'If the game's at 0-0 going into quarter-time, that's something we'd be happy with'.
"We've got the legs to run out games pretty well but that's just a big focus this week that we can't let that happen again."
Westhoff also had some advice for fellow forward John Butcher, who had a return to forget against Geelong.
Butcher lined up for the Power for the first time since round 15 last year, but put two straightforward shots at goal out on the full.
He appeared completely devoid of confidence, although coach Ken Hinkley had Butcher's back post-match, declaring the 11-possession game was "much better" than his lead-in SANFL form.
"He's been out of the game for 10 months now, first game back he's always going to have a few problems," Westhoff admitted.
"At least he's getting opportunity, having shots at goal, he's chasing and tackling and that's what we want from him.
"You've just got to get back on the horse, kick a few footys around ... you just need to go back to the basics.
"Your routine, things like that which help every aspect of your game.
"Talk about your game, talk about your mistakes and that's how you improve."
Harry Thring is a reporter for AFL Media. Follow him on Twitter: @AFL_Harry.
