The 27-year-old striker only joined the club from Monaco in January, but failed to score in all his nine appearances for Saints.
Carrillo’s move to La Liga sees him reunite with former Southampton
car crash manager Mauricio Pellegrino, who became Leganes manager earlier this summer.
This move is unlikely to fill any Saints fans with hope of recuperating the eye-watering sum spent on him in January.
In what looks like a panic buy in hindsight, Pellegrino signed the Argentine £19m, a club-record transfer fee which stands as of writing.
Omitted from the Saints pre-season squad currently on tour in China, it’s thought Carrillo was not being considered to feature in manager Mark Hughes’ plans this season.