King was injured playing at the Emirates Stadium

The 26-year-old picked up the injury in a Premiership match against Arsenal on 14 October that Watford lost 3-0.

"It is a blow to lose such an important players and a great character," manager Aidy Bothroyd told the club's website.

"But Marlon will be back and he will be stronger for it. He'll be in the dressing room alongside us, he will be my assistant."

King's team-mate Ashley Young added: "We're disappointed to lose a big player for the club but we have got to kick on and do it for him.

"It is a big loss but people have to step on and fill that gap. It is disappointing for everyone - for the players and all the staff."