Arsene Wenger blasted referee Craig Pawson for not sending off Florin Gardos as his Arsenal side slipped to a 2-0 defeat at Southampton.
Gardos fouled Alexis Sanchez just outside the box with the Chilean seemingly through on goal, but Pawson only booked the defender.
Sadio Mane and Dusan Tadic had already put the hosts 2-0 up as Arsenal spurned some early chances, but Wenger was furious with the decision not to dismiss the Saints defender.
“We must give credit to their 'keeper today, and as well to the referee that he didn’t give them a red card when Sanchez was clean through,” he said.
If one against one with the goalkeeper isn’t a goalscoring opportunity I don’t know when it would be one.
“That’s beyond my understanding because I couldn’t see for what reason he didn’t do it. If one against one with the goalkeeper isn’t a goalscoring opportunity I don’t know when it would be one.”
Both goals came from defensive errors as Wojciech Szczesny and Laurent Koscielny both endured a torrid afternoon for the Gunners.
Southampton’s win moves them four points ahead of Arsenal, and Wenger admits he was very disappointed with the mistakes they made at the back.
“That made the difference today,” he said. “At our level, in our final third we didn’t defend well. We were quite in control of the game and we gave it away, it’s as simple as that.
“It’s disappointing because the team gave a lot, but you cannot afford these kind of mistakes at our level.
“It’s a shame because we were not under pressure, we were under control, but we go home with no points. Southampton defended well, the keeper defended well, but we can only look at our defensive performance. We had the chances, we couldn’t take them.
“We could have won this game today, and that makes it even worse for us.”