The Champions League holders shot to the top of the Premier League table earlier in the season but a combination of injuries and loss of form has seen Chelsea fall 10 points behind Manchester City.
Ben Chilwell has been ruled out for the rest of the season and fellow full-back Reece James is expected to be out for around two months after his recent injury setback.
With both Chilwell and James spending time in the treating room, Chelsea are ready to sign at least one new full-back during the January transfer window and have targeted Everton’s Digne.
According to The Sun, the European champions are now set to step up their interest in the 28-year-old, who is expected to leave Goodison Park on loan following the arrival of Vitali Mykolenko.
Thomas Tuchel is still able to call upon Marcos Alonso, who started Sunday’s 2-2 draw with Premier League title rivals Liverpool, but is said to want more defensive reinforcements this month.
While Chelsea’s backline has been impacted by injuries, the club have at least tied Thiago Silva down to a new contract.
After Silva signed a one-year contract extension at Stamford Bridge, Chelsea director Marina Granovskaia said: ‘Thiago Silva’s experience, leadership and performances have been and remain very important to this squad, so we are hugely pleased to extend his contract by another year.
‘We look forward to his continued influence as we seek honours this season and next, and more of the qualities that have led to him having such a big impact for us on and off the pitch.’
Silva, meanwhile, said: ‘To play here with Chelsea is a real pleasure. I never thought I would play for three years here in this great club so I’m very happy to stay for another season.
‘I would also like to say thanks to my family, the club, Marina and to Mr Abramovich for this opportunity. I will continue to give everything for this club and for the supporters, who have always been by my side since I arrived.
‘It’s amazing to have this relationship with the fans and not only that but the players, staff and the whole club. I’m going to give everything to keep playing at this level in the most important league in the world.’