Wales boss Warren Gatland revealed that a lack of game time meant Adam Jones had to be dropped for the second Test.
The tighthead prop has been a fulcrum in the Welsh pack for a decade but has been left out to face South Africa in Nelspruit, with Samson Lee getting the nod and Aaron Jarvis providing cover on the bench.
"He hasn't had a lot of rugby recently," said Gatland.
"The way the game was and potentially the way the weather conditions are going to be for this week, we just felt at this stage we wanted to have a look at someone else and to make a change.
"Adam was disappointed with us taking him off and the way he played. We appreciate that as well because of what he's achieved as a player, but it doesn't matter who you are, the expectations are you've got to go out there and perform.
"We are all under pressure to perform."
Gatland also defended the decision to retain Mike Phillips at scrum-half ahead of Gareth Davies, with fans criticising the British and Irish Lion's performance in Durban.
"When we went back and looked at the tape, apart from one loose pass and us looking for him to be a bit more of a running threat, it was one of the most accurate games Mike has had for a long time," added Gatland.
"There were not errors around his game. We just think he needs to be a bit more of a running threat.
"He worked hard, he chased back and saved us a try on one occasion.
"Overall it was a pretty reasonably good performance from him. But we are pleased with Gareth too and we want him to come on and make an impact."