Blues boss Mancini had a wary eye on Saturday’s clash with Chelsea and handed senior debuts to Javan Vidal, Greg Cunnningham, Ben Mee and John Guidetti for the tricky third-round tie at The Hawthorns.
But after Brazilian striker Jo gave City the lead, they conceded two second-half goals to a determined Albion side go out of the competition in stark contrast to last season’s run to the semi-finals.
Mancini said: “We wanted to win this competition but we couldn’t take any risks, both games were important to us. But we play Chelsea at 12.45 on Saturday and have only got 12 or 13 players.
“The time for players to recover is very short. It needs to be three days’ minimum. It would have been better if the Chelsea game was an evening kick-off.”
Chelsea’s Champions League tie on Tuesday precluded that option, and interestingly the champions also went out of the Carling Cup with an unexpected 4-3 defeat by Newcastle United at Stamford Bridge.
But despite the exit, Mancini had no qualms about blooding City’s up-and-coming youngsters. He said: “I gave the young guys their chance in this game, and if they don’t play then they will never improve.
“I knew that there was a chance we would lose with six young players, but we did want to win. Saturday is more important, but if I had not so many players injured, I would have put out a stronger side.”