Central midfielder Nandez could well be a replacement for 21-year-old Italy international Barella, who is said to be closing in on a £45million ($58m) switch to Stamford Bridge.
Boca president Daniel Angelici confirmed Boca have agreed to let the Uruguayan depart for Sardinia, although he revealed further negotiations over the structure of the deal are required.
"We have accepted Cagliari's offer for Nandez because we spoke to the player and he wants to go to Italy," Angelici told Radio La Red.
"What we do not accept is the form of payment and that is what we are working on.
"It will be up to the Italian club to make the effort. At the moment the first instalment of the offer is not enough to pay taxes."
Nandez, who has earned 20 caps for Uruguay, missed the end of the Argentinian season though injury, but appears to have recovered in time for a move to Serie A.
His potential transfer could prove hugely influential as it would provide the necessary back-up required for Barella, should he move to Stamford Bridge.
However, it appears likely that Barella is set sign for the Blues.
The former Barcelona and Arsenal man bid an emotional farewell to the Stamford Bridge crowd during Saturday’s FA Cup victory against Nottingham Forest.
Although Fabregas has not yet confirmed he is leaving Stamford Bridge, he did claim after the match that, “everyone knows the situation.”
Chelsea boss Maurizio Sarri also stoked the fire by admitting that Fabregas’ departure would certainly see him sign a replacement in the centre of the park.
“If Cesc goes, of course, we will need a replacement. Now with the midfielders we are in trouble I think," he said.