Sanchez has been locked in contract talks with Arsenal for a number of months but is yet to reach an agreement on fresh terms.
The Chile international has just 18 months remaining on the deal he signed in the summer of 2014 when he joined from Barcelona.
According to the Daily Mirror, Gunners manager Arsene Wenger has set his sights on Borussia Dortmund forward Marco Reus as a potential Sanchez replacement.
And Italian outlet Calciomercato claim Premier League rivals Manchester City and Serie A giants Juventus could make a big money move for Sanchez next summer if he turns down a new deal.
The 27-year-old has been key for Arsenal this season, scoring eight goals and providing seven assists across all competitions.
The north London club are also said to be in negotiations with German playmaker Mesut Ozil, who is also out of contract after the 2017/18 campaign.