Houllier made eight alterations from the side he started against Blackburn for the Eastlands clash which Villa lost 3-0 - including playing Delph at left-back.
It has left fans angry and venting their frustrations on message boards and radio phone-ins, particularly as local rivals Birmingham have won the Carling Cup.
But Delph believes the players left out needed to recharge their batteries and that Houllier has been consistent in his policy of changing his line-ups all season.
He said: "We're a very good squad and we've got a good squad of players. The changes that got made, they needed to rest. They've been playing a lot of games this season. The players that came in against Manchester City were more than capable of doing a job.
"I don't think it's a case of that we played a weakened team. We played a strong team, players that have been playing all season. The gaffer is confident in our ability and thinks we're strong as a squad. If he's bringing players in, which he's done all season, not just in the City game, I don't see why it should be looked upon as a bad thing."
Source: PA
Source: PA