Kalou has scored four times in Chelsea's blistering start to the new season, which has produced five successive league wins, but he suffered a thigh injury during Chelsea's shock 4-3 home defeat to Newcastle United in the League Cup on Wednesday and was replaced at half-time.
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"They will both have scans on Thursday but they are both doubtful and I am not sure they are going to be fit enough in time," said Ancelotti after watching his side lose a competitive match for the first time since April.
The weekend's other feature games see second place Arsenal host West Bromwich Albion, while third place Manchester United make the short trip to Bolton Wanderers.
Liverpool's defeat to Northampton continued their poor start under new coach Roy Hodgson. They are currently 16th with just one win from five games and dissent is apparent in the squad with defender Daniel Agger criticising Hodgson's tactics in an interview earlier this week.
Saturday's match at Eastlands pits new money against even newer money with City desperate to emulate the success Chelsea have enjoyed since Russian billionaire Roman Abramovich rescued them from penury seven years ago.
Before Abramovich's arrival, Chelsea had won the league just once in 1955, but have now won it again another three times and completed the FA Cup and league double last season.
"I played football myself and I understand why the players who are
