The Gunners won as Gabriel Martinelli's first-half strike hit the post and rebounded into the Shakhtar net via their goalkeeper Dmytro Riznyk. Riznyk later would deny Leandro Trossard from the penalty spot.
Arteta said afterwards: "Well I think there were two very different halves, first one we were very dominant, we created four big, big chances we should have converted them and put the game to bed with the amount of dominance we had, the second half very different, we look tired, we lacked that sharpness with and without the ball to regain the ball in the right moments as well in the right areas and giving certain balls away that allow certain transitions.
"We had two big chances again, missed a big penalty and that emotion again was difficult to overcome and we have to begin but credit to them they are a good side the moment you allow them space, don’t finish actions and give them the chance to run they are a threat. Overall it’s Champions League, get the win, clean sheet. Let’s move on."
On Martinelli, Arteta said: "He looked really sharp, he looked really fresh, fresher than anybody else on that pitch. You noticed that against Bournemouth, you could tell that was different. He had another gear, he added another level of threat, he started the game really well and he had a great performance today."
On Trossard's penalty, Arteta added, "Yes, they made that decision, the penalty taker normally is Bukayo or Martin and after that we have two or three players who can take it, they made the decision and unfortunately Leo missed it, but as you said it’s an opportunity missed."