Nasri has completed his £25 million move from Arsenal to City, and Redknapp believes it is obvious that the midfielder's motives were driven by money rather than a desire to win silverware.
The Frenchman stated earlier on Friday that he decided to exit the Emirates this summer in pursuit of trophies.
"[Man City] have the biggest squad and they showed it last year when they won the FA Cup and finished in front of Arsenal.
"So, the facts talk for Man City. I hope to win titles. I played at a high level with Arsenal but I never won anything.''
Redknapp disagrees, however: "I don't believe that, no. He could have gone to Man United.
"He wanted to go to Man United, that's what I heard. But then Man City came in and offered him more money again so he went to Man City. That's how it goes. It's just a shirt and off we go."
Nasri is the latest in a long line of expensive signings that have moved to the club since it was taken over by Sheikh Mansour three years ago.
With the likes of Carlos Tevez, Sergio Aguero and David Silva among their ranks, Redknapp believes Roberto Mancini now has a squad that is better than European champions Barcelona. For that reason, Redknapp believes City will challenge the Catalan giants all the way for the Champions League this term.
"They will be challenging for the Champions League," he said. "They will eventually be challenging for everything because they have the resources to keep bringing in the best players in the world.
"Eventually if the owner stays with the club, which I'm sure he will, they will win the Premier League. It's a club everyone wants to be at now. It's scary."
Spurs beat City to fourth place two years ago, but Redknapp admits the gap has widened between the two sides and has predicted a hard time for his men in Sunday's visit of Mancini's men.
"They are looking strong. I would say that they have probably got as strong a squad as any team in the world," Redknapp said.
"They don't have Messi but man for man, they certainly have a stronger squad than Barcelona. They have two men in every position who are top-class players.
"You look at that forward line now and they have Aguero, Tevez, Edin Dzeko, Silva - it's amazing. That's an unbelievable goalscoring forward line that could absolutely whip anybody on their day, or on their off day. They will be difficult to contain."