Chelsea target Nicolo Barella is reluctant to move to Stamford Bridge this month.
The Blues are looking to sign a midfielder so they can allow Cesc Fabregas to move to Monaco.
Fabregas agreed a three-and-a-half year contract with the Ligue 1 club this week, but returned to London and will see out the rest of the campaign at Stamford Bridge if Maurizio Sarri fails to land a replacement.
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Assistant manager Gianfranco Zola has a good relationship with his former club Cagliari and that is something which could help in talks over Barella. However, the 21-year-old, who Cagliari value at £45million, is unsure about a move to Chelsea due to concerns over a lack of game-time.
Asked about new signings on Monday, Sarri said: "I don't want to speak about players of other teams of course. If Cesc goes of course we will need a replacement. Now with the midfielders we are in trouble.
"Without Cesc we are only 5 so we are in trouble. We need a replacement of course."