Doolan was presented with his baggy green on Wednesday by Andrew Symonds, while Shaun Marsh edged Phillip Hughes to claim the final spot in the side at No.4 in a reshuffled batting order.
Smith had no hesitation in sending the visitors in at Centurion.
"It's a good opportunity for us to put Australia under pressure," Smith said.
"The pitch does get better and better (to bat on) as the Test match goes on."
Australia captain Michael Clarke said he planned to bat first had he won the toss.
"I think the wicket will have a little bit in it up until lunch, we'll have to bat well," Clarke said.
Shane Watson's calf injury and the omission of George Bailey mean two new faces come into a team that was unchanged throughout the Australian summer.
The pitch is expected to offer uneven bounce, but is nowhere near as green as it was earlier this his week.
Warm weather is predicted for the duration of the Test, with a top of 30C for day one.
Australia - David Warner, Chris Rogers, Alex Doolan, Shaun Marsh, Michael Clarke (captain), Steve Smith, Brad Haddin, Mitchell Johnson, Ryan Harris, Peter Siddle, Nathan Lyon
South Africa - Graeme Smith (captain), Alviro Petersen, Hashim Amla, Faf du Plessis, AB de Villiers, JP Duminy, Ryan McLaren, Robin Peterson, Vernon Philander, Dale Steyn, Morne Morkel.