Posted by Samuel Kalu of Nigeria, a winger, suffered an injury in Watford’s 1-0 away victory over Norwich City at Carrow Road on Monday and is anticipated to miss more time due to it.
Kalu exited the field after the defeat at minute 29.
Seven minutes from the end, his replacement Vakoun Bayo gave the Hornets the winning goal.
The victory was the team of Slaven Bilic’s first in three league games.
Kalu was given his first season-opening start in the contest, but it was disappointing.
Since moving to Vicarage Road, the former KAA Gent player has been hampered by ongoing ailments.
He has only made nine appearances for the London club this season.