Pep Guardiola’s side were stunned in a 3-2 defeat to the injury-hit Canaries on Saturday, which saw them fall five points behind title rivals and table toppers Liverpool.
Without the calming influence of key defender Aymeric Laporte – set to be out for six months with a knee injury – City were all over the place at the back, with defensive errors leading directly to two Norwich goals.
John Stones and Nicolas Otamendi did not look settled alongside each other at Carrow Road, but it was England right-back Walker who was singled out as one of the worst performers.
His poor positioning allowed Norwich to pass their way through the City back-four and score their second goal on the breakaway.
Cascarino told talkSPORT the 29-year-old has not been playing at his best for some time, and predicts summer signing Joao Cancelo to take his place soon.
The Portuguese defender has played just one minute of football since arriving from Juventus for £60million and remained on the bench against Norwich.
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