"It was pretty evenly poised coming into the last day," Williamson said. "Batting last would have posted its challenges, but it was by no means impossible, even with the ball taking turn."
Du Plessis responded by saying that was a fair call but...
"If today was a full day of cricket, with one seamer down [Trent Boult] and one of their main bowlers [Tim Southee] out, we fancied our chances at 191 ahead on a spinning wicket. We felt capable of getting another 40 runs.
"If you can get through someone like Kane early, we'll put some pressure on their batsmen."
The genial duel promises to be a highlight of the series off the pitch. It is a far cry from where du Plessis once stood with the New Zealand team, notably at the 2011 World Cup quarter-final in Dhaka.
The then 26-year-old had made his international debut three months earlier and got drawn into a stoush with water waiter Kyle Mills and New Zealand captain Daniel Vettori. The Proteas were crumbling to defeat after Martin Guptill instigated a run out of AB de Villiers. The trio were fined.
Du Plessis has since redeemed himself but was again punished after South Africa's test against Australia at Hobart in November for using mint-tainted saliva to help shine the ball.
The penalty came when the International Cricket Council brought a case against him. Pictures of his actions were published outside the parameters of matchplay controlled by the umpires.
Du Plessis was found guilty, fined his match fee and lumbered with two demerit points despite an appeal.
The Proteas skipper was asked to contrast that with the stoush which erupted between the respective Australian and Indian captains Steven Smith and Virat Kohli last week during the Bengaluru test. Kohli accused Smith of seeking help from the dressing room with the Decision Review System.
"Us and New Zealand are similar in the way we play," du Plessis said. "We respect each other on and off the field and we play a similar brand of cricket. We don't see that the way you carry on off the field will have an effect on the outcome.
"When you play a team like India and Australia that can happen and it's easy to see how that can blow up. For me it has been good to be on the other side and to see how things unfold. It would have been interesting to see how the Australian media would have reacted to me doing that."
Du Plessis was asked if he was surprised neither captain had been charged by the ICC.
"I was, purely from what I went through in Australia for something that I feel was a lot smaller [in magnitude].
"Maybe it's just because I speak on from a personal point of view and I felt that I was treated harshly, but when you see something like that you hope that it would be exactly the same."