The 24-year-old has been starring for Argentina at the World Cup of late, and has built on the reputation he earned last term in Portugal for his impressive showings.
Liverpool have been heavily linked with him in recent weeks as Brendan Rodgers steps up his plans to draft in a new left-sided defender, but now Chelsea appear to be in pole position.
Reports suggest that Jose Mourinho is ready to spend up to £15m to nab the South American, with top target Filipe Luis’ move to Stamford Bridge from Atletico Madrid stalling.
Sporting are aware that they may well be unable to keep Rojo, and could be tempted by Chelsea’s rumoured eagerness to splash the cash.
Mourinho is keen to replace departed veteran Ashley Cole, and draft in a genuine left-back after relying on right-footed Spaniard Cesar Azpilicueta in the role for much of last season.