Dhoni's form with the bat has been heavily scrutinised in the recent past with every failure being looked upon as an ominous sign.
However, the talismanic keeper-batsman did well in the just-concluded limited overs series against Sri Lanka to silence some of the criticism.
"We are not stupid. I have been watching this sport for the last 30-40 years. Virat has been a part of this team for a decade now. We know, at this age, he (Dhoni) can beat players aged 26. People who talk, forget that they played the game," Shastri told 'India Today'.
The sentiment was echoed by Shastri, who has been vocal in defending Dhoni in the past as well.
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"If they look at themselves in the mirror and ask the question, 'what they were at the age of 36?'. Would they have run two runs faster? But the time they finish two, this guy will run three. Then he has won only two World Cups and averages only 51. Till today you don't have a wicket-keeper to replace him in the one-day team," he asserted.
"He is still one of the best around, not only in the Indian team, but in the world. Some of the things you see with him are not sold in the market. You will not get it anywhere else," he said.
"The fact that he does not play Test cricket, means he should be playing as much cricket as possible till the World Cup in 2019," he added.
Shastri also spoke about the upcoming tour of South Africa, which starts with a three-match Test series from January 5.
"For us all opposition is the same, all oppositions have to be respected and every game is a home match. And as it turned out that next we are in South Africa. Where South Africa is different is that we haven't won a series in South Africa," he said.
"Therein lies a massive opportunity for the team to do something special. The belief is there. We are going there and we will treat South Africa like we treat any other opposition we have played against. There will be respect but we will go there to win," he added.
"The great thing about Virat is his work ethic, his realisation of what kind of player he can become and what he it takes to become that player... And it has become part of his lifestyle.
"What happens is, that when you have a captain in that frame of mind, wanting to achieve things others can only dream of. Then it rubs off on other players. Others want to emulate him. He wants to raise the bar for himself and he doesn't want any room for excuses," said Shastri.
"The most important thing about the team is that this is a team and not an individual. The word 'I' can be thrown out of the window. It is always we. Individuals can stay at home if they are not part of the team culture. No matter how big the individual. That is the difference with this team," he said.