The Citizens manager was left fuming after his side produced an abject performance against struggling Southampton, losing 3-1 at St Mary’s on Saturday evening.
City’s latest defeat leaves them a staggering 12 points behind title rivals Manchester United, and Mancini was unhappy with his squad.
“When you play football and you are a top player, you should take your responsibility. Always. It’s not always the fault of the manager,” said Mancini.
“The players should take responsibility – if they have big balls. If not, they can’t play in a top team.”
Mancini pointed to the international friendlies on Wednesday as a factor in City’s loss, also hinting the Citizens are paying for their failure to sufficiently strengthen in the summer.
“I think we had big problems because we had 15 players who came back Thursday night and Friday from Qatar, Chile, from everywhere. This was the big problem this week,” he added.
“In the end, we did a really bad performance, and for this I’m disappointed.
“We can lose if a team plays better than us. That’s normal. But not like this.
“For a team like us which has won the title, the FA Cup, won the Charity Shield after 38 years, its normal the year after as champions could be difficult.
“But probably because we did some mistakes in the summer and we didn’t improve our team probably But now we have good players and I think we shouldn’t lose a match like this.”