The England international has been struggling with a fever this week and was admitted to hospital.
And Express Sport understands he is a major doubt for the match.
Chelsea line-up predicted to face Tottenham Hotspur in the FA Cup semi-final Thu, April 20, 2017
Express Sport predicts who will start for Chelsea in their FA Cup semi-final clash against Tottenham Hotspur at Wembley on Saturday (5.15pm)
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Who will Antonio Conte pick to start for Chelsea against Tottenham?
Ahead of the match, Conte confirmed Cahill was suffered from gallstones and would struggle to feature at Wembley.
Conte said: “This period is not a lucky period for us. When we started to have the training on Tuesday, he arrived with a bit of fever. Our doctor preferred to take him to hospital, it is not a serious problem.
Chelsea defender Gary Cahill
“He is getting better, he is improving a lot. For tomorrow, it is very difficult.
“He had fever, a problem but not serious. The doctor preferred to take him to the hospital. I don’t know the right words. Gallstones.”