Warner committed a level-two offence in the first Test.
He was speaking after a man of the match performance in South Africa's six-wicket win in the second Test against Australia, but before the verdict from the International Cricket Council was announced.
Mike Hutchings / Reuters Cricket - South Africa vs Australia - Second Test - St George's Park, Port Elizabeth - March 11, 2018.
He added: "As I had said before this game, Rabada and (Mitchell) Starc would be the two bowlers to look out for and they would be the ones to get excessive reverse swing since they are exceptional bowlers". I have to see it as a big learning curve and not repeat the same mistake.
"I'm not happy about it, but time moves on".
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We still don't know whether he will be available or not. "We are a rugby team and no rugby team has an aura of invincibility about them".
Rabada contested the first charge, claiming the contact with Smith was unintentional. ICC rules brought in recently are aimed at stopping any physical contact at all between bowlers and batsmen, though, in an attempt to crack down on incidents that might cause flashpoints in games.
"It's a disappointment because you want to have your best players in the series", said captain Du Plessis.
Rabada missed the second test against England previous year having reached four demerit points.
The 22-year-old Rabada, who took 11 wickets to help South Africa level the series 1-1, was fined 50 percent of his match fee and given three demerit points, which took him past the tally of eight that triggers an automatic suspension.
"It seems to me that one of those more irreversible facts in global cricket is that playing against the Aussies seldom end up as an uplifting experience".
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Match referee Jeff Crowe, who handed down the punishment, said Rabada could have avoided coming together with Smith. We as a team have got no issues with the way the Australian team play their brand of cricket.
He represented South Africa at schoolboy level and at under-19, and won the under-19 World Cup in 2014.
"We don't know where it's come from or where it's going to end", he said.A Neymar return would upset the balance of the team which Valverde has found to keep Barcelona unbeaten in 28 La Liga games.
And Mitchell Marsh was guilty of the same offence after swearing at Rabada once he dismissed him on day four.
This means the Proteas' star paceman will miss the final two Tests of the series in Cape Town and Wanderers in Johannesburg.
South Africa are assured of the second prize of five lakh dollars.
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While no Australian has managed a century, the home side has had two-rookie opener Aiden Markram scoring a gallant 143 in the loss in Durban and AB de Villiers setting the platform for victory at Port Elizabeth with an unbeaten 126.