Didsbury Dave said:
That what I heard too. I cannot see what the fuss is about.
He brought Rodwell on late on because they were getting on top and our two strikers were doing nothing. Putting aguero on then could have cost us a deserved, morale boosting win
That's not what he said (I do agree with the rest of your post though - didn't disagree with the subs personally). Here are the quotes from the Independent for the record:
One more goal would have been enough to secure the two-goal margin needed for City to top the group at Bayern's expense, but Pellegrini, although, it could be a simple case of still learning the English language, appeared to think City required five goals, not four.
When asked by Sky Sports after the match if he was tempted to bring on his best striker with nearly 30 minutes remaining, Pellegrini replied: "I was tempted if we scored the fourth goal of course. That's why I sent Aguero to warm up."
When talking about the substitution of Silva at a time when City only needed one goal to achieve the two-goal winning margin they required to finish top, Pellegrini, who reached the semi-final of the competition with Villarreal in 2006, said:
"[But] to score two goals in those circumstances would be difficult and Silva has to play no more than 70 minutes"
One more goal, City's fourth, could have given them the 4-2 scoreline they needed to finish as Group D winners, but Pellegrini did say later in the interview that finishing top was not the most important thing for his team.