Raheem Sterling has been suffering from sickness and separate back pain as Chelsea's never-ending availability crisis continues ahead of Monday's matchup with Everton at Stamford Bridge.
Mauricio Pochettino explained on Friday at Cobham: "He sent a text last night or this morning, I don't know, to the doctor saying that he was vomiting."
Pochettino also revealed that Enzo Fernandez and Axel Disasi were yet to train ahead of the clash after picking up injuries in the 2-2 draw at Sheffield United.
Ben Chilwell has also had fluid drained from his knee after he took a hefty blow in the dying minutes of England's 2-2 friendly draw with Belgium during the international break.
There was optimism the issue was just a knock but the left-back, who has had a injury-ravaged campaign, was forced to miss games against Burnley, Manchester United and last weekend's trip to Bramall Lane with the problem.
Chelsea hope to have Chilwell fit to face the Toffees, though as of Friday lunchtime, he had not trained with the group. Goalkeeper Robert Sanchez has also been struggling with illness while Levi Colwill, Wesley Fofana, Reece James, Romeo Lavia, Lesley Ugochukwu and Christopher Nkunku also remain sidelined.
Fofana, James and Lavia will not play again this season while Ugochukwu could return to action in the coming weeks having been sidelined since December with a hamstring injury.
Pochettino also swatted aside suggestions that his young team was starved of leaders, citing Sterling, Thiago Silva, Conor Gallagher and even third-choice goalkeeper Marcus Bettinelli as reference points within his dressing room.
He feels in time, talents like Cole Palmer can grow in stature while also highlighting that the excellent £42.5million summer signing from Manchester City is leading in the best way possible - by performing on the pitch.
Poch added: "We are talking about too many players that only arrived this season at Chelsea and arrived in the Premier League. I don't know. If you say, Palmer can be a leader, but he's focused on trying to perform and show that why he's here.
"At the moment, he's doing well. For me, it's perfect because for him it's 'I arrived at Chelsea and I showed that I am doing well'. All players have different objectives. It's like if we talk about Nico Jackson. Nico Jackson, if you compare him with Didier Drogba in the first season, Drogba with Nico Jackson, he's there."
Chelsea are now unbeaten in five home matches in all competitions while their last defeat came back in February when they lost the Carabao Cup final to Liverpool 1-0 after extra-time.