Andreas Christensen picked up a 'small knock' during training on Friday which sees him miss Chelsea's Premier League match against Crystal Palace on Saturday evening.
Thomas Tuchel named his starting eleven which saw Callum Hudson-Odoi come back into the side, but Christensen was a surprise absentee as Kurt Zouma slotted in at the back.
But it has been reported that Christensen, who also celebrates his birthday on Saturday, picked up a knock in training and that is why he misses out.
His knock must have occurred after Tuchel's press conference due to the German stating that they had a fully fit squad for Saturday's clash other than Thiago Silva who is out through suspension.
Tuchel knows this is a chance for the Blues to bounce back after losing to West Brom last time out in the league, but expects a difficult match.
"It gives us no advantage we have a 2-0 lead against Porto when we play against Crystal Palace," Tuchel said on Friday.
"It can give you a huge boost in self-confidence. Tomorrow is not the day to fulfil all our obstacles and reach our goals. Tomorrow is 90 minutes. You just have to focus for 90 minutes. We don’t have to think about Tuesday and Man City.
"We have to start over and over again, and this is the challenge. It’s very important we are fully focused on every challenge we have, forget the games and results we had, accept every new challenge and raise new challenges right from the start."