The midfielder, 32, has suffered a setback in his recovery from a serious knee injury.
Diarra, who was released in the summer and has been training with the club in a bid to prove his fitness, has seen a specialist in Spain and will be reassessed next month.
Cottagers boss Martin Jol said: "He had a setback, first with his ankle and then with his knee. If he is fit, he is still a very good player."
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