"They (Smith, Warner and junior player Cam Bancroft, banned for nine months) have made a mistake, they've admitted that and are disappointed with that action.
"They will have to take that strong punishment and move on and I suppose you always learn from tough lessons and I sure they'll be doing that.
"(But) it is a shame that two fantastic world class players have made a mistake."
And Williamson admitted he had been in touch with Warner by text. But he wasn't revealing the content of those messages.
"We spent bit of time together in the IPL. We know each other fairly well. I sent a few texts, that's about it really."
Under-fire Australian coach Darren Lehmann, who has kept his job for now in the wake of the stunning developmnts during the Cape Town test against South Africa, has said New Zealand play the game the way it should be played.
"For us it's about how we want to play the game, that's important to us," Williamson said.
"It's been part of our environment for some time and we want to maintain that.
"We believe it suits us as people and so we want to commit to that, play as hard and well as we can on the park, but at the end of the day the game finishes and you're still people. That's what we like to try and hang our hat on.
"We certainly don't point fingers. Everyone makes mistakes at times and you do need to learn from those and move on. No one is exempt in that respect."
Williamson praised his predecessor as captain, Brendon McCullum for the tone he set within the New Zealand team.
"He was huge in that respect, setting an environment where we wanted to play the game in a certain way and that was reflective in the way we went about our business on the field," Williamson said.
