The England defender is one of Pep Guardiola's most trusted players, and is often the first name on the team sheet.
Despite being in a great position at City, Walker admitted he does have a career ambition to fulfill.
He wants to return to the Blades, where he began his career, before he calls it quits.
Speaking to the BBC's Friday Football Social, Walker said: "I'll go until my legs don't want to go.
"Until they go I'll keep running. I made it very clear I want to go back and play for Sheffield United.
"I started there, played there from when I was six or seven years old. If I am dropping down and becoming a burden, obviously not. But as long as I am still enjoying it, I'll keep doing it."
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