The pair endured a difficult outing in the Carabao Cup defeat to Liverpool, which ended in a penalty shootout, leaving Chelsea with more questions to answer about the reliability of their defensive options.
For Gusto, the concerns stretch beyond one disappointing performance.
As Flashscore has reported, Chelsea have already begun seriously looking at replacements for the right-back, with doubts growing over whether he can turn around his situation.
Fofana is also facing an uncertain future.
Our sources have revealed that the centre-back is in danger of losing his place at Chelsea in 2027, with the club continuing to assess how they can upgrade figures within the back line.
His struggles against Liverpool added to the concerns, although the bigger issue is whether he can deliver the consistency required to become a reliable member of the side.
Fofana's missed penalty kick will have done little to convince the Chelsea hierarchy that he is on the right track.
Chelsea need defenders who can be relied upon in high-pressure matches and it is anticipated that both Fofana and Gusto will become available on the transfer market.
Chelsea need a strong season and are unconvinced that the duo can meet the standards expected of a club with ambitions to compete at the highest level.
The Liverpool defeat was another reminder that defensive shortcomings can undermine any progress elsewhere on the pitch.