The Cottagers host mega-rich City in the Barclays Premier League in a game that reunites manager Mark Hughes with the club who unceremoniously sacked him just under a year ago.
Defender Kelly, who helped Fulham record a goalless draw at Newcastle on Saturday, told his club's official website: "Manchester City are a good side, and it will be a test for us because they have some fantastic players. But, at Craven Cottage, we are capable of beating teams of any calibre.
"We'll take the positives from the game at Newcastle, get our heads down and work hard in training.
"As always, we will be prepared, and we will go out Sunday and show what we can do. Hopefully, it will be a case of all guns blazing for us."