Arsenal boss Mikel Arteta had mixed feelings after his side secured a 3-1 victory against Olympiacos in the first leg of the Europa League last-16 tie.
Martin Odegaard gave Arsenal the lead with a beautiful strike but a mistake at the back in the second half saw Olympiacos draw level. Just like at Burnley on Sunday, Leno played the ball short and into the feet of Dani Ceballos - fresh off the bench. The midfielder lost the ball to Youssef El Arabi and the forward scored from an empty net.
Gabriel restored Arsenal's lead before Mohamed Elneny, who came in as a substitute scored the third goal for the Gunners.
"I have been saying that for a while, and I can probably see more things because internally I know the process that has happened and how much has happened since we were here a year ago," Arteta said on the team progress.
"I think the difference is really big and we are really pleased with the result and the goals that we scored, and the way that we played in big moments in the game. But as well we have to be very clear and honest with ourselves that we gave three goals to the opponent and they took one, and at that level, they are going to punish you. So to go to the next level, we have to stop doing that and be more ruthless - and when you are that dominant and playing that well, just kill the game."
Arteta was asked if whether the errors shake his confidence in his approach and said, "No, it is just when we have to play it. You know you have to play the ball to this player, but when is the difference… is it now, a second later or a second earlier?"
"That gives the opponent a chance to press or intercept a pass or not and that is where the difference is. To discriminate the decision making and when it has to be done is what dictates in the next action whether you are successful or not. But it is not about stopping or discouraging the team not to play, we just have to understand when to do it and that’s crucial. If not you create insecurity in a game that is totally under control and it brings the team into an insecurity mode because you gift to the opponent how much we have in the game, the chances that we missed and it is unnecessary. But it's true that the reaction after that to score a goal - and we probably should have scored one more - was great to see as well."