England went down to a 100-run defeat by Sri Lanka in the second Test at Headingley on Tuesday to lose the series 1-0 after the tourists clung on for a draw at Lord's.
The Sri Lanka series was the first since Pietersen, England's all-time leading run-scorer across all formats, had his central contract cancelled by the England and Wales Cricket Board.
But hopes results would improve quickly in his absence after the 5-0 Ashes reverse were dashed by Sri Lanka.
And Pietersen, in his latest Daily Telegraph column published Saturday, suggested there was more to England's woes than on-field performance, citing the way in which last man James Anderson broke down in tears after being dismissed off the penultimate ball at Headingley as an example.
"(Stuart) Broad and (Anderson) looked jaded at Headingley. Why? Why was Jimmy so emotional? We have lost a lot of matches in the past but he has never shown such emotion. He has been through tougher times and suffered lower moments but never been in tears before."
"It says to me there is an underlying current of unhappiness. The Australia tour was hard. We were beaten up due to a lot of reasons I cannot go into right now, and some of the senior players are still suffering, with the result that they are struggling to offer leadership in the dressing room," added Pietersen, who signed a settlement agreement that allowed the ECB to terminate his central contract before it was due to expire.
