Both players had to be withdrawn during Sunday's 3-1 defeat at home to Sunderland because of hamstring injuries.
And Jol confirmed that the duo now face lengthy spells on the sidelines.
"It will be at least three weeks for them," he said.
But there is better news regarding Mali midfielder Mahamadou Diarra.
The former Real Madrid star has not played since November 3, but when asked whether Diarra could return for Saturday's trip to Stoke, Jol said: "Could be, yes."