Since reaching the final of the 1992 World Cup, where they lost to Pakistan, England's form at the tournament is the worst of the frontline cricketing nations.
England have won 16 matches since 1992, compared to four-times champions Australia's 38 and better only than Bangladesh and Zimbabwe. They are also the only leading nation not to have qualified for at least one semi-final in that time.
But Pietersen, England's leading World Cup scorer with 575 runs for 13 innings - still only the 31st best of all nations - told the Daily Telegraph ahead of England's World Cup opener against Australia in Melbourne on Saturday that a lack of expectation could work in their favour.
"I really do believe they have an outside chance of winning this World Cup," Pietersen said. "They can play with freedom because nobody really expects them to win the tournament and this should be reflected in positivity throughout their batting.
"England have struggled in World Cups for 20 years because we have played directly after an Ashes and have been mentally shot. There are no excuses this time."
England captain Eoin Morgan replaced Alastair Cook after the Essex batsman was dumped for a lack of form late last year, but since scoring 121 against Australia in a tri-series match on Jan. 16, the 28-year-old has scored zero, two, zero and zero runs in his next four innings.
However, Pietersen thinks Morgan's style of captaincy is more in-tune with the demands of modern 50-over cricket and will provide England with plenty of inventiveness with bat and ball.
England will certainly need to be more aggressive with the ball after claiming 25 five-wicket hauls since 1992. That ranks them eighth, with Pakistan on 52 and Australia on 54 leading the way.
England's batsman have also struggled during the last five World Cups, making just four centuries compared to current holders India who have hit a swashbuckling 18. Again England are ranked eighth on that list, ahead only of Zimbabwe
"Morgan will be positive. That is the way he plays and you always captain how you bat, which means taking risks," Pietersen said. "I like the way he has rotated his bowlers and set his fields.
"You need confidence when deciding how to use your bowlers, a key tactic, and an ability to make wise decisions when pressure mounts. That is when you need a calm leader such as Eoin,” he said.

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