Smith did not train at Saturday's optional session at Newlands, with the majority of last week's side also sitting out the hit.
The 37-year-old has endured a frustrating tour of South Africa, with scores of 25, 27, 28 and 3 across the first two Tests headed into the Cape Town decider.
Smith looked the best of all Australians in the first innings at St George's Park last week, before a neck issue caused significant discomfort and limited movement.
He is expected to be the centre of attention in Cape Town this week, with Australia's last Test there resulting in his year-long ban out of the ball-tampering scandal.
Much larger crowds are also expected at Newlands than at the first two Tests in Durban and Gqeberha, with Smith all but certain to cop some attention.
But Australia believe that will only spur the veteran on.
"He'll be fine. I think he showed that in 2019 in England (where Smith averaged 110.57 on his return from the ban). It'll be nice to have a crowd," Travis Head said.
"He handles it well. Sometimes, it brings the best out of him as we've seen in the past.Â
"I'm hearing good things about Cape Town so a good atmosphere is always good. We support him. I think he's been through a lot in that space."
Head's comments echo those made by Josh Hazlewood, who in the lead up to the tour also pointed at Smith's run-spree in the 2019 Ashes.
"We saw him come back at Edgbaston that time after 12 months out and get 100 in both innings, so he has that in him," Hazlewood said.
"He always wants to do well. Look out if he has that sort of feeling again."
Former Test captain Allan Border also warned Proteas' players and local fans not to provoke Smith before this series.
"He'll want to just really make as many runs as he can, and if they poke the bear by taunts and stuff, he could become a real thorn in their side," Border told AAP.
"Because he's just such a good player.
"If he's got that laser focus, he becomes doubly difficult. And he's a great player, anyway."
Meanwhile, South Africa have confirmed speedster Anrich Nortje won't play in the third Test, after limping off St George's Park last week with a groin complaint.
The Proteas have not added another player to their squad, leaving Corbin Bosch the most likely replacement with Gerald Coetzee and Dane Paterson the other options.
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