The match on Wednesday is the first of three fixtures at the same Durban venue in five days before the teams play five One-Day Internationals in the build-up to the Cricket World Cup in India, which starts on October 8th.
Australia have a host of players either injured or unavailable for selection, leaving plenty of opportunity for new faces.
Short will partner Adelaide Strikers teammate Travis Head at the top of the order and Marsh has tipped him to make a big impact.
"It’s very exciting, he is coming off an outstanding 12 months for the Strikers and Victoria last year and thoroughly deserves his place," Marsh told reporters on Tuesday.
"We are looking forward to seeing him open the batting. I have encouraged him not to change anything and take the game on."
Josh Inglis will wear the wicketkeeper gloves in a side packed with all-rounders who can contribute with the ball, though Marsh said they would concentrate on their specialists.
"I would be very surprised if we used nine bowlers, if we do then something has gone terribly wrong," he said.
"It is important that we have a lot of bowling options and flexibility, but we have our five or six main guys to do the job for us.
March said he was also keen to see Johnson take on the South Africans with his express pace.
"He is a super talent. He bowls mid to high 140s and swings the ball. My only message for him is to make sure he enjoys it.
"We are quite focused on playing the way we want to play. There are some fresh faces in the team but we have confidence they can all play at international level."
South Africa will also have a side with several new names and Marsh believes that makes the series even more intriguing.
"It is not too often you go into an international series not knowing too much about the opposition, but we have done our homework and it is always exciting when young guys debut in international cricket," he said.
Australian team:
Matt Short, Travis Head, Mitchell Marsh (captain), Josh Inglis, Marcus Stoinis, Tim David, Aaron Hardie, Sean Abbott, Nathan Ellis, Adam Zampa, Spencer Johnson
