Former South African cricket captain Graeme Smith has called David Warner a fool while adding Nathan Lyon may regret his unnecessary celebration following AB de Villiers' run out in the Kingsmead Test.
The first Test in Durban provided a major talking point on day four when star batsman de Villiers was run out by Warner and Lyon without scoring.
Australia's vice-captain then unleashed a spray on centurion Aiden Markram, who was involved in the run out, while Lyon dropped the ball in the direction of de Villiers who was sprawled on the turf in trying to make his ground.
"The Aussies were pretty fired up at that time pushing for a victory," Smith told cricket.com.au in Durban, where Australia need just one wicket on day five for victory.
"But he (Lyon) is an experienced cricketer.
"I think he'll probably say it was unnecessary himself.
"We've got used to Davey over the years. I think the less interest you take in him the better.
"He can be a bit of a fool at times. It's best just to let him be."
Smith warned the teams not to cross the line with sledging.
"I think everyone that's played the game has hard moments and that's what makes the hundred from Markram so special," Smith said.
"He's had to work, he's showed great composure, the Aussies were all over him after that run out.
"Everyone wants to be competitive, people love watching that.
"I think there's always a line that you've got to be careful you don't cross."
Australia require just one wicket to take a 1-0 lead in the four-Test series after setting South Africa 417 for victory.
The Proteas are 9-293 with Quinton de Kock (81) and Morne Morkel (0) at the crease.