City have failed to offload a raft of fringe players who Mancini has deemed surplus to requirements.
A City insider told the Sunday Mirror: "Unless there is some movement of players out of the club in the next 10 days this promises to the biggest test of Roberto's management skills that he has ever faced.
"There is a group of players set to report back to the club who have been made aware that he doesn't rate them and he doesn't want them around the place.
"The big question is how will he manage players? What will he do with them because they aren't part of his plans and he won't want them in and around the first-team squad?"