Celtic 1-2 Ferencvaros: Neil Lennon says side must blame themselves
The Scottish champions trailed to their Hungarian counterparts but levelled through Ryan Christie before conceding late on to drop into the Europa League.
The defeat follows last term's home exits at the hands of Cluj and FC Copenhagen in continental competition.
"We seem to have made the same mistakes as last year," Lennon said.
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"The first goal we can maybe legislate for a little bit, but the second goal is really poor decision-making.
"I don't know if it's attitude or mentality but it's cost us again. I'll have to carry the can, and take the responsibility for it."
David Siger put the Hungarian champions in front early on but although Ryan Christie's deflected strike levelled the one-legged tie, Tokmac Nguen's breakaway goal saw Celtic knocked out.
Celtic were beaten 4-3 at home by Cluj of Romania in the Champions League third qualifying round last season, then lost 3-1 to Danish side Copenhagen in the Europa League last 32 in Glasgow.
Both were ties Lennon's side were expected to win, just as they were against Ferencvaros, who instead have consigned them to Tuesday's Europa League third qualifying round draw.
"The game was actually a lot easier than I thought it was going to be, but we didn't take our chances and we had plenty of them," Lennon told BBC Scotland.
"I'm not saying Ferencvaros are a bad team - they're not - but we had so much control we should have won. That doesn't make us weak, it doesn't make me weak, but people will cast aspersions."
Asked what message he would give to his players, Lennon added: "Get your mentality right, get your attitude right. If some of you don't want to be here, leave."
Asked if his impression was some players don't want to be at the club, he responded: "In some cases."