Watford's Mauro Zarate suffered an anterior cruciate ligament injury against West Ham United on Saturday.
Zarate, a January signing from Fiorentina, twisted his knee awkwardly towards the end of the first half of the 1-1 draw against his former club.
The winger needed oxygen and nine minutes of treatment on the pitch before being carried off on a stretcher and taken to hospital for scans.
And on Sunday the 29-year-old revealed the extent of the damage in an Instagram post.
He wrote: "With sadness...