Craig Levein's men drew their opening Group A games at Hampden against Serbia and Macedonia, and consequently have already dropped four points. Following the trip to Cardiff, Scotland are away to Belgium next Tuesday night in the second part of October's double-header which could make or break the Scots' chances of reaching Brazil.
However, Dundee United boss Houston, speaking at Scotland's Mar Hall base on the outskirts of Glasgow, would not concede that the Scots need to beat the Welsh to keep their qualification hopes alive.
He said: "I don't think you ever concede anything."
He continued: "What you have to make sure of, and I've said it before, is that we have to try to get as many points as we possibly can. Cardiff is another opportunity.
"There are three points up for grabs and we will try to get three and we will try to get three in Belgium.
"I wouldn't put any targets on how many points we are going to get out of the next two games. I just think that when three points are available, we have to try to get those three points."
Wales lost their opening two matches against Belgium and Serbia and are as equally desperate for a win as Scotland.
However, Houston believes teams in the section - which also includes Croatia - will all take points off each other during the course of the campaign.
He said: "There are a lot of teams in this group who are closely matched and I think there will be points taken off each other. Wales will take points off teams as well.
"There will be games where people will think 'that team will win that one' and it doesn't happen."