Peter Siddle says spooking batsmen is one thing, causing concussion quite another.
Ryan McLaren was on Tuesday ruled out of the second Test in Port Elizabeth, where Australia can seal their first Test series win on foreign soil since downing the West Indies in April 2012.
McLaren was suffering from post-concussion syndrome, brought about by a brutal Mitchell Johnson bouncer that drew blood in the first Test at Centurion.
WATCH THE BRUTAL DELIVERY IN THE VIDEO ABOVE
Siddle noted McLaren's ill-health didn't sit well with any of the Australian pacemen.
"On the field it's hard and aggressive, but when you see things like that happening it is a little bit disappointing," Siddle said.
"You don't want to hurt anyone in a way that they can't come up (for the next match).
"It's not as if you're trying to do it. At the time you're just obviously trying to build a bit of pressure and get a wicket."
Left-armer Wayne Parnell is expected to take McLaren's spot in the hosts' XI for the second Test that starts on Thursday.
"A couple of the netties (net bowlers) were left handed so it gave the boys a bit to look at there," Siddle said after training on Tuesday.
However, if South Africa selectors opt to shore up their batting order then left-hander Dean Elgar could come into contention.
Elgar made a pair on Test debut, against Australia in 2012 when Johnson twice dismissed him at the WACA.
Beanpole Morne Morkel suggested the squad had full faith in Elgar, who was 12th man for the first Test and dropped a catch provided by David Warner when the eventual centurion was on 26.
"Dean is like a Staffy. He's tough as nails. I'm sure if he gets the nod he'll be more than capable of doing the job," he said.
"It's a tricky question (who replaces McLaren)."
The Proteas are expected to retain spinner Robin Peterson, who was largely unthreatening in the first Test.
Morkel described Johnson's short ball to McLaren as part of part of the reason cricketers love the sport.
"Spectators also love that sort of bodyline action in Test matches," he said.