Giteau was a high-profile omission from the Australia side for Saturday's Tri-Nations opener against South Africa, with the 92-Test veteran dropped following the shock defeat to Samoa.
Giteau was always likely to make way for first-choice No.10 Quade Cooper but he was expected to still be included on the bench.
However, Giteau has been axed completely, sparking debates over whether he will now make the World Cup squad.
Deans, though, said: "Well Gits is part of the (Tri Nations) squad so he has a big part to play. We prepare as one and next week's another week.
"You can look at anyone and make assumptions but like I've said many times, we're presuming nothing going forward.
"Matt will obviously want a role going forward, he has a role going forward, we just don't know what that will entail just yet in terms of playing."
Quizzed on his decision to axe Giteau, Deans, who has opted for a five-two split of forwards and backs on the bench, said the ability of both Kurtley Beale and James O'Connor to cover the playmaking role meant the veteran's services were not required.
"We've got good versatility in our backline, we believe we've got what we need there so we've opted to carry a little bit more up front," Deans said.
"We've obviously gone for a combination that we think will be good for us and we believe we have the capability within the existing group to cover all of those potential permutations around 10 and 12."
Meanwhile, the coach confirmed prop Benn Robinson has opted against having the ruptured anterior cruciate ligament in his right knee repaired in a desperate bid to return in time for the World Cup.
"Robbo isn't going to proceed with his operation, his knee is remarkably stable for an ACL injury...so he's opted to give it a go and attempt to play without an ACL," Deans said.
"A typical ACL injury involves medial ligament damage as well, his didn't and he's got good stability.
"There's a little bit of laxity as a result of the fact he doesn't have an ACL ligament, but it's not significant, it's even consistent with some (people) post-operation.
"To put it in perspective, it is a low percentage success rate if we base it on history, so I wouldn't be jumping through hoops just yet, but he's opted to give it a go.
"I understand there's one player who's played a Test match without an ACL, but he played in the midfield and it wasn't a great experience.
"But the midfield's distinct from up front, I mean Robbo might just have to park his sidestep for a while."
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