The champions were rampant against his side, winning 6-1 at Etihad Stadium on Sunday.
Huddersfield lost the opening round match at home to Chelsea as well, but the manager is now looking to turn things around.
"In the end, it wasn't a tactical decision which decided the game, it was just the quality we faced today," Wagner said. "With the problems we had before the game, it didn't make it easy for us and we have to say congratulations to City for a great performance, we were not good enough today.
"For us now, the season starts. We hoped for more out of these two games, we could not expect more from these two games even if we didn't want to have a heavy defeat like today, but now the season starts.
"We're focused, we won't get too upset from this result, the good thing is we had this last season where we lost heavy defeats and the character of this group is to move forward."