The Serie A side are already assured of their place in the last 32 as Group F winners, having gone unbeaten in their five matches so far.
With top spot secure, Mancini will use the clash in Baku to give playing time to some of his fringe players, as well as those making comebacks from injury.
"Even though this game doesn't count towards the standings, there are some players who had less time on the pitch than the others, and some who are emerging from injuries," he told SportMediaset.
"So they need to play so they can put some minutes into their legs, and they can become useful for the games in the future. It's going to be an important game.
"[17-year-old Federico] Bonazzoli is one among many, we took several young players here.
"They're all very young and I think some of them will get some playing time.
"There are some players I still haven't seen because of injury, too, who were not in a condition to play.
"For some of them this is going to be an important game."
