Arsène Wenger lamented naivety and a lack of maturity from his Arsenal team as they conceded a damaging late winner to Borussia Dortmund to change the complexion of their Champions League group.

The manager was already unhappy at the manner in which they had handed Dortmund the initiative, when Aaron Ramsey erred in the build-up to Henrikh Mkhitaryan's early goal. But, having got themselves back into the tie to look the more likely victors, they were undone by Robert Lewandowski's finish on an 83rd-minute counterattack.

"We put ourselves on the back foot with the first goal and were a bit naive with the second goal," Wenger said. "If you look at the number of saves our goalkeeper had to make and we conceded two goals, then we can only look at ourselves. We were not mature enough. If you cannot win a game, then don't lose it. In the second half we were on top but we made it difficult by giving them the second goal."

Wenger complained that Lewandowski might have been sent off for a 64th-minute elbow on the defender Laurent Koscielny, although he also admitted that some of his players had been off-colour against a team that he described as "physically" the best they had faced this season.

"It looked like Lewandowksi could have been sent off," Wenger said. "I haven't seen it well, honestly, and the referee was in a much better situation. I will have to look at it again.

"I'm disappointed. It was a game of high intensity but very few chances. Dortmund were well organised to stop us playing and we were not as good as we can be offensively. Some of our players were not as fresh as they can be physically.

"I felt we started a bit hesitant, which we didn't do against Napoli [in the previous tie], which gave them confidence. I believe our flowing football going forward was not quick enough. We were not at our best."

The defeat leaves Arsenal level on six points with Dortmund and Napoli but having played two of their three ties so far at home. It means they are likely to need a big result on the road against Dortmund or Napoli. "The group is tight," Wenger said. "It's difficult for us, but possible. We need a result away but we can do that."

Jack Wilshere caused alarm when he landed heavily on his right foot in the first half and he took a couple of further knocks before his substitution on 58 minutes. "At the moment his desire to play absolutely gets him through the game but he was handicapped," Wenger said. "You could see that Jack was not completely himself, which is why I decided to take him off. We'll see how he responds in the next two or three days. We'll have to wait for the medical assessment."

Wilshere said of his injury: "I jarred it. My ankle stopped and my body went over it but I've done that before, even before I had surgery [to the foot]. It was painful for five or 10 minutes and then I ran it off. I will have treatment because it is still a bit swollen but I should be all right for the weekend."