The German playmaker was absent from the matchday squad for the first three games of the Premier League season having been involved in a carjacking attempt by an armed gang in London, though made the bench against Spurs last time out.
There were fears over both his safety and that of Sead Kolasinac – who was also in the vehicle and fought off the attackers – but Emery is happy that he can call on Ozil once again.
Asked why he picked the World Cup winner at Vicarage Road, Emery told Sky Sports: He trained with us in pre-season and he was playing good, but with the circumstances we could not play with him.
But now hes playing, hes training with a normal attitude for three weeks, and he can help us today. Everyone is important, the first XI, the players on the bench, we really need them all.
Arsenal take on a Watford team that has undergone some major changes in the past week, with Javi Gracia axed and Quique Sanchez Flores returning to the club.
There werent any real tactical surprises in Flores first line-up since taking over, and Emery does not believe the change of manager will be a decisive factor in the game.