Wales shipped eight tries in their 55-23 loss to New Zealand, while Argentina were at their nuggety best in a one-point win over England at Twickenham.
When able to keep their discipline in check, Argentina are a match for anyone with powerful forwards and dangerous runners in the backline who will test what was a porous Wales defence against the All Blacks.
"Clearly as a group, we want to get the result," Pivac told reporters on Thursday.
"At 22-16 and 29-23 (against New Zealand), we’d done well to work our way back in but we put ourselves under pressure.
"It’s more about our defensive work in our 22. The boys know that. We’ve been a lot more physical this week. We’ve got to make sure we’re ready for what’s coming.
"They’ve (Argentina) knocked off a lot of big teams. England have been added to that list. They’re very physical and they’re starting to score some good tries."
Pivac does love to tinker and will start with regular winger Louis Rees-Zammit (21) in the fullback position on Saturday, though that is down to an injury to Leigh Halfpenny (33).
He has also dropped stalwart lock Alun Wyn Jones (37) from his matchday squad.
"It’s an opportunity before the Six Nations and World Cup to give Ben Carter a chance," Pivac said of Jones’ omission. If they’re called upon in the Six Nations or World Cup, they need to be exposed. We think this is that opportunity.
"We set goals for the season and Alun is no different. Each player is reviewed and we’ll talk on goals."
Argentina coach Michael Cheika (55) has kept an unchanged side as he targets another big scalp having also defeated New Zealand and Australia this season.
Hooker Julian Montoya (29) leads a team containing five players who started the comprehensive 33-11 win over Wales in Cardiff last year.
"We’ve been working on self-belief, understanding what we can do and what we are capable of and making ourselves go to the new standard and get better," Cheika told reporters.
"We’ve put together one or two results on the road this year but with time in between. Now we can try and win away for a second successive weekend."
