Manchester City's Papa John's Trophy group campaign was brought to a halt in midweek.
The City Under-21s were beaten by Rotherham, despite creating several good chances to score.
Brazilian youngster Kayky also made his debut for the team, but he did not have enough of an influence to impact the result.
Rotherham went on to score five goals in the second half, winning the game at a canter.
Kieran Sadlier did the most damage to City's youngsters, netting three times.