He tells Bill Lothian in today's Evening News: "The world rankings are quite new and generally all that is taken on board is who is up at the top or ahead of your team.
"So it is not a big consideration - other than the fact that we have to start climbing," admitted the Glasgow skipper after referring to Japan's position.
The Japanese are moving forward albeit their latest leap encompasses one place from 18th to 17th.
John said: "Japan are not that far behind us. Had Nathan Hines not got his arm under the ball to prevent a fifth Australian try before half-time which would almost certainly have opened up a gap of 35-0 then I don't know if we'd have managed to fulfil a commitment to go on from there and out-score these opponents but the reality is we did.
"So momentum is available and in taking advantage there is no doubt that Japan will be shown every respect at a venue which should provide a cracking atmosphere for top rugby as I know from experience."
John, who came on as a half-time replacement for his 32nd cap added: "Whether it is Australia, South Africa, New Zealand or Japan who provide the (Autumn) opposition we will prepare exactly the same.
"We have recent experience of facing Japan (32-11) at the last World Cup so that encounter will be drawn upon with advantages stemming from taking the game to Perth.
"I have played there for Glasgow Caledonian Reds against the likes of Leicester in front of a near-capacity crowd of around 8000 and the atmosphere lifts players.
"Not only are Scotland on the way back and eager for a win that will provide more impetus going into the remainder of the Abbey Autumn Tests against Australia at Hampden Park and South Africa at Murrayfield - a win with a quality performance would be great and is the aim - but fans can surely benefit from watching a Test in a smaller arena where the atmosphere, also, makes it worth travelling to.
"That said, we aim to provide the win but the McDiarmid Park factor with its fine playing surface and close proximity seats should not be underestimated as an attraction that can bring the best out of both teams."
Latest world rugby rankings: 1 - New Zealand; 2 - Australia, 3 - England, 4 - France, 5 - South Africa, 6 - Ireland, 7 Argentina, 8 - Wales, 9 - SCOTLAND, 10 - Fiji, 11 - Italy, 12 - Samoa, 13 - Romania, 14 - Canada, 15 - Uruguay, 16 - USA, 17 - JAPAN, 18 - Portugal, 19 - Tonga, 20 - Morocco, 21 - Korea, 22 - Georgia, 23 - Russia, 24 - Chile, 25 - Ukraine, 26 - Namibia, 27 - Czech Republic, 28 - Hong Kong, 29 - Germany, 30 - Tunisia.