Arsenal manager Mikel Arteta has expressed his confusion at the decision to disallow a goal for his side in a 1-0 defeat to Leicester City in the Premier League on Sunday.
Alexandre Lacazette thought he had headed the Gunners in front after just four minutes at Emirates, only for the linesman to flag for an infringement.
While the France international was onside from the corner, Granit Xhaka was ruled to have impeded Foxes keeper Kasper Schmeichel from an offside position.
That ruling would prove decisive as Leicester scored the winner via Jamie Vardy in the 80th minute as Arteta's side failed to make the most of their statistical dominance.
Speaking to Sky Sports, Arteta said: "I’m really disappointed, we had it in our hands in the first half and I don’t know how the hell the goal was disallowed.
"They caught us with space at the back and in that moment we lost the game. It is difficult to create spaces with 10 men behind the ball, but we should have finished the game better. When it comes to those moments you can’t give away chances at the back.
"We still had some moments after the goal but gave away too many free kicks. The effort that the boys put in, and the pressure the Leicester team put you under, it’s not an easy thing to do but we have to improve."
The result sees Arsenal drop to 10th in the Premier League, while Leicester have risen to fourth after six games of the new season.
"The game the way it went, I felt we had total control in the first half and restricted them to nothing. We were winning every ball, created a few chances and scored a goal I don't know how it got disallowed," Arteta added to BBC Sport.
"They defended deeper in the second half, waiting for the mistake and in one moment they did it. Against this block, against so well organised teams, when you open them up you have to put the ball in the back of the net. They were similar against Manchester City, they scored with two set pieces and credit to them for what they have done but our players responded and I feel sorry for them.
"We have so many alternatives in the team and can have fluidity. It worked in some moments and there are options we can manage."