Newcastle qualified in second place and now have two months to get ready for the knockout stages.
Ameobi, 31, said: "There are no excuses, we were not up to speed. It was very disappointing. Our inexperience perhaps told in the end with the boys chucked in at the deep end.
"At times that has worked out well for us in Europe but this was a step too far.
"But we are through and we are delighted. We want to stamp our mark on Europe.
"Hopefully we can look forward to February with a fully-fit squad and really attack with all guns blazing.
"We know how good those Europe nights are."