The 23-year-old pulled his hamstring during a training session last week and he is yet to recover from the injury that kept him out of the Hornets’ goalless draw against Brighton and Hove Albion last Saturday.
Success has played 23 matches in the Premier League this season with a goal to his name.
His last outing was against Tottenham Hotspur when he was introduced for Gerard Deulofeu in the 63rd minute as the Hornets bowed to a 2-1 loss at Wembley.
Ahead of this weekend’s tie against Everton at Vicarage Road, the Super Eagles attacker is among the three players set to miss the tie as the Hornets aim for their 10th win of the season.
'He (Pereyra) is not ready yet. Maybe next week but not for this game,” Gracia was quoted as saying by Evening Standard.
''Sebastian Prodl is recovering as well along with Isaac Success. He's not ready yet. Roberto, Isaac and Sebastian are out this weekend.''
Watford are eighth in the league table, level on points with seventh-placed Wolverhampton Wanderers with 34 points from 25 matches so far.