Buchanan, who won three out of four Ashes series during his six-year tenure with the Aussie team, had earlier said that Pietersen had the potential to be "a major problem" during the Ashes if he did not halt the alarming slump in form which has seen him go 27 Test innings without a century.
Reacting to the 57-year-old's comments, the English middle-order batsman said, "I didn't react to it (Buchanan's comments) because it was strange that he made headlines. I'm not interested in what he has to say. Who is he? He's a nobody.
"He had the best team to coach in the history of cricket. Anyone could have coached that team. He has done nothing else solid so I won't even take it with a pinch of salt," he told 'Press Association'.
After his successful coaching stint with the Australian national team, Buchanan joined the Indian Premier League (IPL) franchise Kolkata Knight Riders as coach but it did not work.
He got sacked after the team fared badly in the first two seasons under him.
He drew criticism from every quarter for inducing more controversies in the team than confidence. In fact, his complex theories caused harm to the side.
Besides, he also got involved in a blow-up with the skipper of the first season, Sourav Ganguly, who was unceremoniously dropped from leading the side in the second season on the behest of Buchanan
