Richards is also attracting interest from Italy, but £5m could get him to stay in the Premier League and Newcastle are interested.
The Magopies are keen, but they want to off-load Steven Taylor first.
With Pablo Zabaleta and Bacary Sagna set to battle it out for the right back spot at City, Richards will have to leave to find first team football.
Alan Pardew worked with Sinclair at Charlton and has tried to sign him in the past.