Dhoni dropped himself down the order in CSK's failed chase of 217 against RR.
Chasing 217 to win, Dhoni came out to bat in the 14th over and remained unbeaten on 29 off 17 balls with three sixes but his side lost the game by 16 runs.
After the match, Dhoni defended his decision of not promoting himself up the order, saying CSK wanted to try out different combinations and they can always go back to their strengths if things don't work out.
But Pietersen said he is not “buying into this nonsense."
"Yeah, you got to get up. You have to at least give yourself the opportunity to win the game. That's what Sunny is talking about," he told Star Sports during a post-match analysis show.
"When you see how close they went, Du Plessis started to go, then MS Dhoni started hitting at the end and then they lost by only 16 runs.
"So we were talking about a 4 or 5-over period when they were just knocking it around, knocking it around and running silly singles. They could have caught the game up there with a little bit of intent. They could have easily knocked this score off. If you need 20 in the last over, you can win this game.
"It's not about experiments, saying 'oh it's early on in the tournament'. Let me tell you, T20 cricket can bite you very, very quickly. You can end up losing five games on the go very quickly and then you can end up thinking 'oh my goodness, are we actually going to get into the finals?'. I am not buying into this nonsense."'
Indian batting legend Sunil Gavaskar was also left mystified by Dhoni’s decision making as the latter sent the likes of Sam Curran and Ruturaj Gaikwad ahead of him.
"We can't surmise that in the previous, he sent in Sam Curran ahead of him and Curran got 18 off 6 deliveries. Curran did well again, he hit a couple of sixes.
"And then I thought he might come in after that instead of sending young Ruturaj Gaikwad because when the opposition has got 216 means he has to start playing his shots from the word go. It's not going to be easy for him. If the opposition had got 160-170, then by all means, send in Ruturaj so he can maybe play himself in.
"But coming into bat after 5 wickets is like he had decided this match is not going to be won. And that's no way to approach any target. You got to go in with the belief you will be able to win it," Gavaskar said.