Arsene Wenger gave a blunt assessment of his side's performance after Arsenal suffered a 2-1 defeat against Watford at the Emirates Stadium.
First-half goals from Younes Kaboul and Troy Deeney helped the Hornets earn their first ever Premier League win over the Gunners as the hosts suffered a blow to their title aspirations.
Alex Iwobi's strike halved the deficit after half-time but Arsenal could not recover from a poor first-half display which saw them fail to register a shot on target and Wenger, who is serving the second game of his four-match touchline ban, does not believe his presence on the sidelines would have made a difference.
"I don't know, it's very difficult to know, it would be an excuse," the Arsenal boss said when asked if he could have influenced the outcome from the technical area.
"We prepared for the game well. We were warned that Watford would come and make it very physical. Looking at the preparation, I have no basic regret on how we prepared for the game.
"Did we think subconsciously that we could just turn up and it will work? I don't know.
"But from the stands, I agree with you that our first-half was not at the level that we wanted. I don't think we have a physical power problem. We were not mentally prepared, we were not mentally ready to deal with these duels that we usually do.
"You don't make 47 points in the Premier League after 23 games if you have no physical power, but you have to switch it on at 100% in the Premier League, that's what it's all about.
"I am responsible for the results of the team so I am frustrated that we did not win. What the other teams do does not matter.
"What you want is to win the games and I am very frustrated not to win the game.
"We are at home and we have a great opportunity, of course it's frustrating and we have to learn from that, respond quickly and in a very convincing way."
Wenger was also adamant that his decision to drop Theo Walcott to the bench was the right one. Walcott returned to the side with a hat-trick against Southampton last weekend but the Frenchman insists the forward was not ready to start having missed training on Monday.
"He played in the second half," Wenger added.
"If you look well at his history, he has not played for five-and-a-half weeks. He was stiff still yesterday. I kept him out of training yesterday. We have three games this week.
"We know well, do not think we are completely stupid in the way we make decisions. I think it was a good, normal decision."
Meanwhile, Watford boss Walter Mazzarri dedicated their win to the late Graham Taylor. The former Hornets manager died two weeks ago and the Italian gave a special tribute during his post-match press conference.
"Before the press conference finishes, I wanted to say that I want to dedicate this victory to a great person that was Graham Taylor," Mazzarri said.
"We wanted to do it before today (against Middlesbrough) but I think today was a great game and I want to dedicate this victory to him and to the fans as well.
"It was, for sure, a great game but I also had other important games in my career but I also remember at home was with Napoli against Chelsea. But I also don't like to live off the past. Now I'm in Watford and this was, for sure, one of the greatest."