Julio Cruz, Zlatan Ibrahimovic and Luis Jimenez struck for Inter and Mancini, on his birthday, declared: "It was a wonderful gift and I thank the lads, especially as this was by no means an easy game. It was very difficult up until we managed to break the deadlock.
"We did fairly well in the first half, but Zico put them out so well tactically and Fenerbahce are a good side. Once we managed to open the scoring, some spaces opened up and it changed."
Mancini surprised many before kick-off with defender Cristian Chivu pushed up in a midfield position.
"It is Chivu's first time in that role and so we need to work on it more, but it went well. We wanted him there as an extra help for the defenders to close down Alex, who tends to float around and causes problems," explained Mancio.
"Dejan Stankovic was back after a long time off, so we didn't want to strain him too much as he is not yet match fit. He was allowed to move around depending on where he was needed in midfield.
"It was important to secure qualification tonight because we won't have another break until Christmas. It was crucial to go to Eindhoven without that pressure and allowing us to rest a few players.
"In Serie A we have to push all the way because there are going to be some tough games and we cannot afford to slack off."
Marco Materazzi was again given some minutes late on as the defender continued his comeback.
Mancini added: "Every now and then we experiment with a three-man defence and it is something we could use, but we need to work on it first, as we're still a bit rusty. It is an option, though."