Sidwell was Fulham's best player in a grim season for the club where he has been the top scorer in the league with seven goals.
He said: "We have been down there before. Last year there were games we needed to win to get ourselves clear and we always did that. We knew we had that fight and the belief.
"But this year it just wasn't there. And of all the days for it not to be there, on Saturday against Stoke when we needed to go and win, we didn't show that passion and that fight.
"There is one thing getting relegated with courage and giving 110 per cent. If you can hold your hands up and say: 'I have given everything and we have got relegated and we couldn't do any more'.
"But to go down in that manner that we did on Saturday - defenceless really - was very poor."
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