Santon joined Inter on loan from Newcastle in the 2014-15 season having fallen out-of-favour on Tyneside, and made the switch a permanent one last summer.
However, he has had little luck in his homeland with regards to playing time and is set to return to the North East of England instead, with Sunderland having agreed a deal worth around £3 million for the 25-year-old.
Santon will now head to Wearside to undergo a medical and discuss personal terms with Sunderland in a controversial move.
Left-back cover, finally
Only a few players have sported both the red and white of the Black Cats and the black and white of the Magpies, with the rivalry running deep in the North East. The reception Jack Colback receives at the Stadium of Light after leaving for St. James' Park highlights this perfectly.
However, the man who made 94 appearances for Newcastle over the course of four years will finally give Sunderland the cover at left-back they so crave, and fans cannot argue with that.
Patrick van Aanholt grew into a terrific talent as the season wore on last term, but Santon will provide Sam Allardyce with another option in this position and competition for the Dutchman.
Naturally right-footed but preferring to play on the left, the Italian can also comfortably play at right-back - a position that lacks a certain starter after DeAndre Yedlin's loan came to an end.
Adam Matthews looks certain to leave the club this summer while Billy Jones has fallen out-of-favour, so Santon's potential arrival will calm the nerves of the Sunderland faithful for the time being.
Whether Yedlin will follow him to Wearside, however, remains unclear, with this deal perhaps throwing that move into doubt.