Their seventh successive win came courtesy of Craig Cathcart’s 81st-minute own goal and a strike soon afterwards from Mesut Ozil, and after Isaac Success had squandered a fine chance to give the visitors the lead.
Arsenal continue to show signs of progress under their new manager but as in recent victories over Cardiff, Newcastle and Everton they were not leading at half-time.
Similarly to against Everton they also could have lost had Watford capitalised on an encouraging display by taking their chances, and Emery said: “We need more moments in the 90 minutes for this control.
“The first half was not easy but our defensive moments were good. They were more than we wanted but we did well in the first half.
“In the second half, we scored two goals but we conceded two good chances for them. We need more control, we need to continue to improve with the control, with the possession, with the positioning.
“But it’s not easy. Each match is very difficult. I am happy because we are becoming more competitive.
“The ball was near our box for a lot of moments and the rhythm of the match is not particularly what we want. Our players in the first half were a little nervous and we need to continue in being calm.”
Petr Cech suffered a suspected hamstring injury in the first half that Emery expects to keep him out for the coming two to three weeks, leading to Bernd Leno making his league debut, but when asked if Leno could retain his place, the manager responded: “He can convince me, but not now.
“He played because of an injury to Petr Cech but I am very happy with him. He has waited for his moment.”
Following four league victories from four, Watford have secured only a single point from a possible nine despite continuing to impress.
Had substitute striker Success given them the lead, an away win would not have been an unjust outcome and their manager Javi Gracia said: “I am very upset for my players because they deserved more; a better result.
“We had a very good performance, with more shots, with a lot of clear chances to score. We deserved more. I’m sure the right results (will come).
“We are competing well in all the games. All the players are frustrated because they think we will be able to get a good result playing here. They have played well but, as in the last games, we feel we deserved more.
“I am very proud of my players. They have played well. Only the result was bad but the performance was very good.”