Dunne was forced off in the 1st half of last Saturday's 2-0 defeat at Reading and needed 9 stitches in a gashed shin.
Ball, who was covering at centre-half with Micah Richards and Nedum Onuoha already ruled out for the Blues, then suffered a twisted knee in the 2nd half but had to play on as City's 3 subs had already been used.
Ball and Dunne are doubtful for Sunday's home clash against Spurs, although Sven's injury problems may be eased by the return of Onuoha from a hamstring injury.
"Michael Ball is almost certainly out, and Richard Dunne is 50-50 at the moment," said the City boss.
"Nedum will start training with the rest of the group on Thursday, so hopefully he will be OK. Micah, of course, is still out but that is the situation at the moment.
"We can't take any decisions just yet, and hopefully Richard will be available. Vedran Corluka will probably play at centre-half, together with Onuoha."
If Ball and Dunne both miss out and Onuoha returns, then City's defence is likely to be Sun Jihai, Corluka, Onuoha and Garrido.
City's defending of late, especially without Dunne in the 2nd half against Reading, has made our early-season solidity a distant memory.
So Sven knows how important it is to have the City skipper back.
"Richard's a tough guy, and if there is any chance he can play against Spurs then he will do," he added.
"Not only have we not scored recently, we have conceded some easy goals and we need him, and the others, to be fully fit. We were not doing that in the 1st half of the season, which is why we had so many good results."