"They were spot-on. I thought the way the Indian seamers showed us how to bowl. The pace that they bowled, the consistency that they bowled, the skill that they showed, outclassed us as a fast bowling attack. There is learning for us in that when we playing the subcontinent that our style of bowling is not successful," he said.
"It shows that our structures are not where they need to be. The gap between domestic cricket and international cricket. If you look back three or four years and if someone had the vision of saying, in three or four years' time there will be a lot of inexperienced guys. A lot of 34, 35, 36 year olds could possible retire. So what do you do to make sure you get yourself ready for when that time comes?
"And possibly we are guilty of not planning or when these guys going at the same time. And now you've got to replace not only one player but four or five of your best players. Perhaps we could've been a little bit smarter in our planning phase, and the phasing out of the great players," he said.
When asked about the future plans, du Plessis said they will have to rebuild the side.
"It's a rebuilding phase. You have to start identifying characters that will drive the team forward. You look for personalities within a team that you see in 3-4-5-6 years to come. And then the process starts. It's a tough place to start right at the beginning.
"The process will probably take a little bit longer. So for me, our next journey now is trying to make sure that we get a lot stronger as a cricketing team mentally. So if there's work that needs to be done in that department, then so be it," he opined.
He said that the series has left mental scars for the players.
"A tour like this reveals that there's a lot of mental scars that can happen and then obviously it's difficult to come out of that hole.
"It's just a relentless, ruthlessness the way they put big totals on the board every time. The effect it has on you mentally as a batting lineup, it takes a lot of energy and it takes a lot of toll and that's why you could see towards the end our batting was mentally weak. You don't want to be mentally weak," the skipper pointed.
"We played our best match in the first Test and the consistent pressure that was on us made us weaker every Test match that we played. That therefore tells me that we're not mentally strong enough as a team and that some work is required on that department," he signed off.