Right-back Richards is now fit and available having missed out for the goalless draw at West Brom on Boxing Day due to the calf strain he suffered in the recent 3-0 win against Stoke.
Left-back Kolarov is also coming back into contention after six games out with a groin injury as City boss Roberto Mancini has a strong squad to select from at the Stadium of Light.
And the Italian has vowed to test his squad's depth to the full as the game at Sunderland is followed by the visit of Liverpool on January 3, before an FA Cup third round tie with Manchester United next Sunday.
There is also a two-legged Carling Cup semi-final with Liverpool and Premier League games against Wigan and Tottenham before the end of the month.
Mancini said: "It is impossible to play in two days with the same players, this is sure. January will be a key month. We will have important games - FA Cup, Carling Cup, four in the Barclays Premier League.
"I think this month will be very important."