It is understood the Championship side, who have former Saddlers midfielder Erhun Oztumer among their ranks, have been placed under the embargo as they owe money to at least one outstanding creditor meaning that the trio cannot play unless permission is granted by the English Football League (EFL) and Football Association (FA).
Dialogue between the club, and the two associations is expected to continue today with a view to resolving the issue ahead of kick-off. Doidge and Matthews both initially joined on loan deals which were set to be made permanent in January, while O'Neil arrived on a short-term contract in the summer which is now due to be renewed. However, the trio will be ineligible to play on Saturday if the club's debts remain outstanding.