"We didn't play well. Perhaps we were too worried about the fact we had a totally new defence. Yet on the field the opposite was true, as the defence held out well, but we were not attacking enough," said Mancini.
"We pushed forward more in the second half, but Fenerbahce could have easily scored another and so they deservedly won.
"The first half was not so awful, it was a balanced encounter and they had the better of the overall play, but we should have done more with the four or five counter-attacks."
Mancini saw second-half substitutes Luis Figo and Luis Jimenez inject some energy into his team and added: "These two options were for substitutions and I could've done it at half-time. They came on quite early into the half and were fresher than the others, but I don't think that made the difference.
"It will be important for us to recover those players who at the moment are out.
"I don't know if getting a slap is healthy every now and then. It's true that nothing is compromised and we still have an excellent chance of going through, but we cannot always start in this manner."