The 24-year-old picked up the injury towards the end of City's narrow 1-0 victory, pulling up and holding onto his knee without any other players close by.
He was stretchered from the field while wearing an oxygen mask and there was some concern that he might have damaged his knee ligaments, which could have ruled him out for the rest of the season.
However, although there has been no official announcement from City, it is believed the England international has had an operation to mend a torn knee cartilage and will be out for up to two months.
The unfortunate Richards had only returned to action at the start of October, after picking up an injury while on duty for Team GB at the London Olympics.
And he was criticised by boss Roberto Mancini last week because he criticised City's tactics during their 3-1 Champions League loss at Ajax.
City are facing something of an injury crisis this weekend because, although he should be back in training soon, David Silva is unlikely to be fit for Saturday's trip to West Ham.
Pablo Zabaleta, Javi Garcia, Maicon and Jack Rodwell are also doubtful and James Milner will be suspended.
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