"Of course, it is very frustrating," the 24-year-old told arsenal.com. "We gave a lot on Tuesday and had to give a lot again at Wigan. It was not easy because it was difficult conditions. But it was important to stay focused defensively and offensively. I think we missed a little bit although we were unlucky.
"The pitch was horrible but what can you say? It was the same for both teams. Of course we like to play and we had to play more long balls so it was more difficult for us.
"But you cannot moan. You just have to score goals and we didn't so now we have to work harder in training and be ready for Middlesbrough [on Saturday].
"It's always difficult especially after big games like Milan, you need to be 200 per cent concentrated. But we had five days to recover.
"We missed a little bit in the final part. But it's like that sometimes. We have the quality and we are strong so we just have to keep going."