Investigations have revealed that Mendi has ruptured the anterior cructiate ligament in his knee, the same injury that sidelined Juninho for the best part of a season.
It's not only disappointing to the club, but also a massive blow to the player, who has started to show why he cost Lazio £30m four years ago. Sadly a reunion with his old club in the UEFA Cup will now be missed.
After a couple of weeks recovery it is likely that Mendi will visit the same clinic in Amercia where Juninho underwent an operation on his knee.