Some have questioned Caulker's decision to quit Spurs, who could be challenging for the title this season, for an almost inevitable survival scrap.
But Caulker, who spent the 2011-12 season on loan at Swansea, said: "It's more of a challenge here than it would be at Spurs.
"I understand people thinking I've stepped down. But coming here feels fresh and I am not looking back.
"If we beat City, it will send out a message to the rest of the league that this club and the players that are here are ready for the fight."
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