Sehwag would be making his 100th Test appearance when he takes the field against England here tomorrow in the second game of the ongoing four-match series.
"The crucial decision that he made in his career was when he decided that he will open the innings. I think that was a big challenge for him but he accepted it. His stats are one of the best stats that you can see. He is someone who is very different to a lot of individuals. His thinking is entirely different," Dhoni said at the pre-match press conference here today.
"How he takes up or faces a particular kind of challenge is very different."
The 34-year-old Sehwag is on the verge of becoming only the ninth Indian player to reach the 100-Test club list, which his idol Sachin Tendulkar tops with 191 under his belt.
"He has got a very important role right from the very start. He is someone who can play shots right from the very first delivery, which means if the bowler is off target, he looks to put pressure on the bowler," Dhoni said.
"We have seen once the batsmen get after the bowlers and if they score a few boundaries off the bowler, then it is very difficult for them to get back into the game," he added.
Dhoni said Sehwag is always full of positive energy irrespective of his form with the bat.
"When you talk about the mindset, that is why he is so special. Whether he is in form or not in form, it does not really bother him. He just keeps thinking positive. He was working a lot on his batting but still his approach remained the same," said Dhoni. MORE