The 57-year-old admits that the Dutch goalkeeper is struggling with a shoulder injury, which has limited his participation during training sessions for five weeks and counting
|6/5||Fulham are 6/5 with Bet365 to beat Cardiff City this weekend.
The Dutch goalkeeper signed for the club during the close-season but injured his shoulder during his debut against Sunderland last month.
He has been on the sidelines ever since and Jol is not sure when he will be able to call on the 31-year-old again.
Stekelenburg has been able to take part in some aspects of training but his participation has so far been limited, amid concerns over aggravating the problem further.
"If it is not right in two weeks' time, then he will probably need an operation," Jol said.
"It’s already five weeks now, so it's certainly long-term. He had a few injections in his shoulder and it's quite sensitive.
"He trains but when he stretches he feels a lot of pain, so we have to be very careful."
David Stockdale has deputised for the injured goalkeeper so far this season but has only kept one clean sheet as Fulham have made a stuttering start to the campaign.