Chelsea boss Thomas Tuchel has revealed an infected wisdom tooth was the reason behind Mason Mount's recent absence as the midfielder eyes a return against Burnley.
Mount missed the last two matches, which came against Newcastle United in the Premier League and Malmo in the Champions League, through illness.
Tuchel has elaborated on what caused the problem and also discussed the England call-up Mount received despite his recent absence from the league leaders' team.
"It's a tricky one," Tuchel said when he was asked about Mount ahead of Saturday's home top-flight clash with Burnley on Saturday.
"Mason was ill but the reason was his wisdom tooth, this was the reason for the feeling [unwell], a bit of an infection.
"Then he was back in training and lost a bit of weight as he couldn't eat properly. He takes medication and let's see.
"He is in the squad for Saturday and can play some minutes, but we will need to wait for the reaction because it seems proper treatment has to be done."
Mount, who scored a hat-trick against Norwich City the last time he started a match on October 23, could join up with England at some stage in the international break.
But Tuchel was not sure whether it would be from the start or even at all, with matches against Albania and San Marino coming up in World Cup qualifying.
"If everything is okay [then he will join up], but we need a proper treatment, so it can be that he is out or he joins a bit later," added the German.
"We will always push and encourage him. We are proud when he is selected, he is proud.
"So there is nothing going on behind closed doors to keep Mason here. There is something going on we need to take care about."
After 10 matches, Chelsea lead Liverpool by three points at the top of the table.
They face Burnley having won their last four Premier League games against them, scoring 12 and conceding twice in that run, but Tuchel is not expecting an easy ride.
Marcos Alonso has been added to the Chelsea injury list, while forwards Romelu Lukaku and Timo Werner remain out along with midfielder Mateo Kovacic.
Tuchel said: "Marcos injured himself in the very last minute of the Malmo match.
"He tried to come out for training but the stress is too high on the ankle. Nothing big but too painful at the moment.
"We know exactly what we'll get from Burnley, they have a clear identity, a manager that has been in charge many years. It will be a tough one."
Asked when Lukaku could return, Tuchel said: "We have the international break now and then we will be more clear. We will see what is going on during the second week of the international break."
And his stance on the football calendar was clear amid debate over the likes of Mount and Callum Hudson-Odoi, who has rejected a call-up for England's Under-21 team.
"There are too many international windows, too many competitions, too many games for the top players," he said. "That increases quantity and not quality. It's too much, simple as that."
Chelsea have scored 16 goals in their opening five home Premier League games this season (W4 L1), their joint-most at this stage of a Premier League season.
The Burnley clash will be the 30th league game for Tuchel at Chelsea and he has racked up 18 clean sheets over the course of his first 29.
Jose Mourinho is the only Premier League manager to keep more than 18 in his first 30 games in charge in the competition (22).