The Gunners boss said that he believed his players showed the “desire and willingness”, despite enduring another disappointing loss at home.
However, Sky Sports pundit Keane thought the Arsenal side look too “soft” right now.
“I think a lot of the players aren’t good enough,” said Keane. “I think there’s a softness there.
“I think, obviously a few years ago all the cheerleaders were out when they had a decent performance up at United.
“Only got one point since then, obviously lost the other two games. I think they look soft.
“They’re probably lacking a bit of confidence, I didn’t see that fight that the manager was talking about.
“I know it was a difficult interview, you’ve been beaten in the game, it’s difficult, but I didn’t see that desire, that determination to get a result.
“You can have an off night, of course, but you still find a way to get a result and at this moment in time I don’t see it with this group of players. They look a bit soft.”
Arsenal have now lost three games in a row in the Premier League, and Arteta admits that he is concerned by their current form.
“A really bad result,” said the Spaniard after the defeat. “The performance, in the first half we had our moments, they had two shots on target and they scored twice.
“We had a great reaction in the second half, we went all for it. I think the team showed a desire, how much they wanted to win the game.
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“We created opportunities, we created chances and the goal didn’t arrive. Obviously disappointed because I think we deserved more from the game.”
“It is (a concern) when you lose three games in a row for different reasons at home.
“Obviously I’m really concerned, I’m responsible for that, but I must the reaction that the team had, the way we played the second half.
“I expect from them more quality and more ability but in the end, the desire and the willingness to go and get a result was there.”