Wales will drop outside the world's top eight teams if the Wallabies triumph.
And that would mean Wales entering next Monday's 2015 World Cup pool draw as a tier three nation, considerably increasing their degree of difficulty when the tournament comes around.
"We've really got to pick our game up this week and try to get that win," said prop Jenkins, who is set to win his 94th cap on Saturday.
"It's all about getting out on the field and imposing ourselves early doors.
"We've let teams get on top of us. Argentina and Samoa knew they had a big chance of beating us, and we let New Zealand get on top of us early.
"There is no excuse for losing three games. We came back in the end last Saturday, but we are disappointed in the way we let the All Blacks get a 33-0 lead.
"Everyone will say that winning makes a massive difference.
"It's just a case of picking ourselves up this week and getting through the things we need to work on."
Wales head coach Warren Gatland will announce his starting line-up later on Thursday, with a minimum of two changes guaranteed.
Cardiff Blues prop Scott Andrews is favourite to take over from Aaron Jarvis, who suffered a season-ending knee injury against New Zealand, but lock Bradley Davies' replacement appears a little more uncertain.
Davies, left with severe concussion after being hit from behind by All Blacks hooker Andrew Hore during the opening minute five days ago, could see his place go to Ian Evans if Evans shakes off a knee problem.
Aaron Shingler, who went on for Davies, would be another option, as would versatile Ryan Jones, provided he recovers from a head injury in time.
Elsewhere, Gatland will have been monitoring the fitness of wing George North and centre Jamie Roberts, who both have hip injuries. North missed the All Blacks clash, while Roberts went off in the 19th minute.
Prop Paul James and utility back James Hook, meanwhile, are both with their clubs - Bath and Perpignan, respectively - and unavailable as the Wallabies fixture falls outside the International Rugby Board's autumn Test window.
Jenkins and Andrews, if selected, will be expected to cause problems for Australia's often-criticised scrum.
But Jenkins added: "They did very well against England recently, and that is the performance you judge them on.
"They've got some quality boys coming through, and we knew in the summer (Wales lost 3-0 in their Test series against Australia Down Under) how tough they are in that area."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.