"It's obviously been a pretty long road and it's pretty satisfying to be in the position I'm in," he said.
Mitchell admitted there were "a number of times" he thought his cup dream was gone - "the first being five seconds after it happened".
However after having MRI scans on the ankle he received his first bit of positive encouragement.
"The surgeon said ... 'you haven't done it as badly as you could'.
"To get through those long, tedious days I really had to hang onto the fact I was a chance."
His most recent test was on Australia's end-of-year European tour last year, when he grabbed three tries in the Wallabies' 59-16 tonking of France in Paris.
Mitchell had 80 minutes, and two tries, for the Australian Barbarians against Canada last month, which helped to get his match legs moving again.
"It's been a bit of a journey and one I've never had to contemplate before.
"I'm somewhat proud of myself to get back to this position. Now I've got to get out and do a job on the weekend as well as part of the group."
Mitchell, with 55 tests behind him, gets the spot vacated by James O'Connor's elevation to the starting XV replacing another injury concern, Digby Ioane. Ioane has had an operation on a broken right thumb but remains in the squad.
"He will return," Australian coach Robbie Deans said.
"It's just a matter of following his rehab and he'll re-enter when he's good to go."
But Deans is pleased that Mitchell's determination to make it back has had a good outcome.
"It's great for Drew," Deans said. "And it's a good story for him to have got himself into the squad. It's a big achievement."