Fulham lost a number of key players including Clint Dempsey and Mousa Dembele towards the end of the summer window, and injuries have not helped since.
The loss of striker Bryan Ruiz is a big one for the Cottagers and Mahamadou Diarra could be heading to the Africa Cup of Nations next month as well.
"If you would have told me in May that in December Bryan won't be there through injury, Mousa and Clint had gone, I would have thought it would be almost impossible," Jol said.
"Luckily enough we brought in some quality players but they play up front most of the time, like Dimitar Berbatov, Mladen Petric, Ashkan Dejagah and Hugo Rodallega.
"Of course we will always look to strengthen, but the January transfer period is not an ideal one.
"The good players will stay at their clubs or you can't afford them because clubs are asking too much money, but we will come up with something.
"We'll look to strengthen the squad because if Diarra goes I can do nothing about it. As it is now he will go to Africa. He was so good for me last year because a lot of older players left the club. He changed the dressing room.
"I can remember him when he was 18 he was a revelation. He started in Crete and then came to Holland with Vitesse. There won't be a lot of players in Europe who will stay at Real Madrid for five years so that is how good he is.
"It was a gamble because he was 30 so it's important to keep him fit."