Springboks head coach Jacques Nienaber said the team's squad system was a major factor in a 32-12 win over Argentina in their opening Rugby Championship match in Gqeberha on Saturday.
The Springboks made 10 changes in their starting team, which Nienaber said was part of a plan to manage a challenging schedule.
"We are playing five big Test matches in a row," he told an online news conference. "The new guys were nice and fresh."
He said, though, that the players left out on Saturday after winning a series against the British and Irish Lions over the previous three weekends played an active role in the preparations for the Argentina game.
"I don't like the word 'rest'. The guys who didn't start today didn't rest. They had a role to fill in preparing the team. It's not like they train less. They just play a different role," said Nienaber.
That role, he said, was in "playing Argentina" in game-simulation situations.
"We are only now a third into our season so we will have to box smart in how we try and keep players fresh."
Nienaber said Argentina were worthy opponents.
"This was only the second match they have lost since the World Cup (in 2019).
"They have played the All Blacks twice, they have played Australia twice and they have played Wales twice. And Wales are the reigning Six Nations champions. They are a tough team to break down."
The Springboks play Argentina again at the same venue next Saturday before travelling to Australia and New Zealand for their remaining fixtures, starting against Australia in Sydney on September 12.
Nienaber paid tribute to the Springbok squad for the way they refocused after their success against the Lions.
"On Sunday we had a couple of beers. We enjoyed it, but we knew we were going straight into the Rugby Championship. The work that the players put in was awesome."
Argentina captain and hooker Julian Montoya said his team would need to work hard during the week with a focus on the setpieces and their kicking game.