Milan were beaten 4-0 and went out 4-2 on aggregate.
"It's the end of a dream. We were not up to it tonight. We suffered from the start and it wasn't the performance we needed," confessed Ambrosini.
"It is a learning experience, one we gladly would've avoided. I can only hope it can serve us well for the future. Now our objective is to get back into the competition.
"We won't have the strain of other Champions League games, so at least now we can focus only on Serie A."