Arsenal boss Mikel Arteta was perplexed by how VAR dealt with a penalty claim during his side's 1-0 loss at Manchester City.
Raheem Sterling scored the only goal midway through the first half at the Etihad Stadium, where Arsenal played a full part in an absorbing contest.
Arteta bemoaned a trio of clear-cut chances that went begging before the break, City goalkeeper Ederson standing firm to twice deny Bukayo Saka before saving from Pierre-Emerick Aubameyang.
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When defending a corner in first-half stoppage time, Kyle Walker's boot came close to Gabriel's head and Arteta questioned why a more thorough video examination of the incident did not take place.
"That has to be checked," he told Sky Sports.
"They said that they checked, and I said, 'How the hell have you checked if you took two seconds to check that action?'. Obviously, there is something there."
Despite ruing those missed chances, former City assistant Arteta had plenty of praise for how his team approached the match.
"I am upset because I think we deserved more from the game," he said. "I am extremely happy with the performance we put in against a top, top team, to play with the courage we did and to make it as difficult as we did, I cannot demand much more from the players.
"When you have three big chances in this game, you have to score. I think the three of them were really good chances and then the situation we have with Kyle Walker from the corner."
Arteta added: "We've come a long way. I'm extremely happy. I was in that dressing room for four years and I know what it takes for a team to do what we've done here."
Saturday's defeat leaves Arsenal in fifth place in the Premier League standings after five matches, the Gunners recording three wins and two defeats in their opening fixtures of the 2020-21 season.
Arteta's charges will be back in action on Thursday away to Rapid Vienna as they kick off their group campaign in the Europa League.