Diarra has not featured for the Cottagers this year and is facing a third operation on a persistent knee problem which has hindered his progress at club.
The 31-year-old former Real Madrid midfielder, whose contract expires in the summer, has made just eight appearances for the Londoners this term.
Diarra has not featured since December 1 last year and manager Jol said: "It is still painful. I think it will be quite complicated without an operation to get him going and fit again.
"We need to sit down and talk to the surgeon and make a decision, but I think he will out for the next couple of months.
"He was the main man last year when he came in. He gave us a boost again and was one of the most important players.
"It was quite a boost for us to get a player of his quality, but you have to be fit. If he isn't fit he can do nothing for us."