Wilder has moved on to other targets, but says it will be hard to bring anyone in because of the wages they are demanding.
The Blades boss admits he may have to stick with what he has, although the window for signing players from the Championship does not close until October 16.
"We're trying to replace Jack, but if we can't then we have to find a solution from within," said Wilder.
"We can't go out and write a cheque for whatever money. And we also have to keep an eye on the wages.
"There are players who go out for very little, seemingly in terms of a fee, but the wages are incredible. The numbers you wouldn't believe."