"Defensively, the mistakes they've made have been punished and they haven't been tough enough mentally to handle this," he said.
"Hibs were well assisted with the goals tonight from our point of view. The game was over after the first 15 minutes.
"It's a shame because they work hard and play some good football. We played some good football tonight and created some good chances but in this league you've got to take your chances as Hibs did."
Jefferies had hoped his effort would see the Pars beat the drop, adding: "If it didn't then we'd lick our wounds, go down and prepare to build a side with some of these boys and others to come back up in one go.
"A lot of these boys would probably do well in the First Division."
Jefferies praised the "fantastic" Dunfermline supporters and said they kept with the side right to the end of the game at Easter Road.
"They've been very supportive and made me feel welcome," he added.
"They knew that if it didn't work out then they know I'll work extremely hard to bring this club back up in one go."
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