"South Africa are definitely better for the fact that they have been battle hardened over the last two weeks, there is no doubt about that," says Deans, who is set to lead his side against South Africa for the first time.
"South Africa have played in two very fast Test matches which were played in that way from start to finish, so they will hit the ground running. I don't think fatigue will be a factor at all for them.
"It is important for us to spend a little longer contemplating what we are about to enter. This will be a significant step up for us from the Tests against Ireland and France."
Deans commented earlier in the week that the space for Rickie Januarie's match-winning try in Dunedin came about as a result of the Springboks' willingness to attack the wide channels, and the former Canterbury Crusaders boss has reiterated that belief this week.
"They are now a little bit more prepared to use the width of the ground, and to be fair that makes them harder because you can't presume. It makes them a more challenging opponent to defend against.
"As long as it doesn't sting us, I warm to their philosophy to expand their game. For sure, it makes them a more formidable opponent."
Despite comfortable back-to-back wins over the French, Deans insists his side have no illusions as the to the size of the challenge facing them at the Subiaco Oval, especially as a second away victory would put the Springboks in pole position to claim the Tri Nations crown.
"This is a very good, mature Springbok side. They not only have achievements behind them but they are still stacking them up.
"They have a lot of experience and they are still in their prime and still hungry for it. They want to stack away silverware so that's a pretty powerful combination.
"They are getting on a flight after this match and heading home and they have a huge opportunity, if they can get up in this encounter. If they do that, they will really place themselves in a magnificent position to close the deal (on this year's Tri-Nations)."