The 24-year-old Croatian has been at Stuttgart since 2018 and has become one of their more important players over the years.
His current deal, which he signed in 2020, still has three years left on it but there is speculation over his future at the club this summer.
Chelsea are amongst the clubs who have been keeping tabs on him and he also has suitors in Germany, where Borussia Dortmund are interested.
And according to German magazine Sport Bild, Sosa’s contract contains a release clause, which could let him leave the club this summer.
It has been claimed that there is a buyout clause of €25m mentioned in his contract with Stuttgart.
If a club decide to trigger it and Sosa wants to move, Stuttgart would have little choice but to watch him move on.
Barcelona are also amongst the clubs who have an interest in the defender, but they are continuing to wrestle with financial issues.