The Brazilian left-back has been on the radar of the Premier League clubs since last summer, with Chelsea coming close to finalising a deal for the defender only for the Italian club to block the move.
Antonio Conte continues his search for a left wing-back and has made Sandro his top priority to provide competition for Marcos Alonso. Chelsea could make a move in January but will have to meet Juventus' valuation, which was £80m ($106.7m) in the summer, and that was mainly done to deter the Blues' advances to sign the defender.
Chelsea, however, will not have it easy in their pursuit of the Brazil international, with Jose Mourinho also a big admirer of the defender. Left-back has been a problem area for the Red Devils boss since taking over at the club and he is looking to bring in an experienced player to solve his problems. Both Chelsea and United have been linked with moves for the Brazilian for a fee of £60m.
Luke Shaw, who was recruited by United in 2014 from Southampton, has failed to meet expectations and is not trusted by Mourinho. He has used a number of players at left-back, including winger Ashley Young.
Mourinho's primary target is Danny Rose, but his high £50m valuation and Tottenham Hotspur's reluctance to sell has made him turn his attention to other players. The club's hierarchy, however, are keen to not spend heavily in this window and have identified more economical alternatives for the manager to consider.
United's stance and Juventus' high asking price is likely to give Chelsea the edge in the chase for Sandro, but it remains to be seen if a move will materialise before the end of the current transfer window.
Marotta confirmed that they are aware of interest from "big clubs" but revealed that no negotiations have taken place so far.
"The policy of Juventus is that if a player asks us to leave, we will not hold him back," Marotta said, as quoted by Goal.com.
"On Alex Sandro, we know of the interest from big clubs, but at the moment, we have not engaged in any negotiations."
Juventus are said to be open to allowing Sandro to leave as they have identified Bayer Leverkusen left-back Wendell Nascimento Borges as a potential replacement for the Brazilian.