Holland international Stekelenburg picked up a shoulder injury in the opening day of the season win at Sunderland and was forced off late in the game.
The injury forced Stekelenburg to miss last weekend's defeat to Arsenal and the Capital One Cup win over Burton, but Jol was hoping he might be back to face Newcastle on Saturday.
However, Stekelenburg has picked up a new shoulder problem in training and he has been sent for scans to find out the full extent of the injury.
"He fell on one shoulder and was out, and now he fell on the other one," said Jol.
"He's in hospital now and will take some pictures and monitor the situation.
"We will try again tomorrow to see if he can join us, but I don't think he will.
"Hopefully it's not serious."