Chelsea pair Thiago Silva and N'Golo Kante have both tested positive for coronavirus.
The European champions have already dealt with one outbreak at the club's training ground with at least six players returning positive tests during December.
Silva and Kante have now joined that list and will definitely miss Wednesday's fixture at Tottenham Hotspur and Saturday's FA Cup tie with Morecambe.
Speaking to the club's official website, Tuchel said: "It's huge for us because they are two huge players. We had the last information today in the morning, so it is quite challenging, but we will push. The guys who are here have our trust and our belief."
While both players were in contention to start versus Spurs, they each would have realistically missed at least one of the upcoming two matches.
The pair will, theoretically, be available for selection for the return leg against Spurs if they produce two negative tests, but that is unrealistic with neither player in a position to take part in more than one training session at best.
