Mikel Arteta has handed Shkodran Mustafi an Arsenal lifeline, telling the defender he can have a future at the club if he cuts the mistakes out of his game.
The German centre-back's calamitous back-pass in the first half of the Gunners' 2-2 draw at Chelsea on Tuesday resulted in his defensive partner David Luiz getting sent off against his former club.
It was the latest in a series of errors that helped to see him fall down the pecking order under former boss Unai Emery.
But asked if Mustafi could have a long-term future at Arsenal, Arteta said: "When he is my player and when he is training with me the way he does every day, of course.
"The plans maybe in the summer were different with him. I came here, he is here and his attitude is always right and he wants to help.
"Yes he made a mistake, but it's OK. I like more the reaction and I look more at the reaction."
While Arteta acknowledges Mustafi has been at fault at times, he says the most important thing is the 27-year-old is not cowed by his errors.
"I don't believe that at 27 you cannot improve certain aspects of the game; I really believe you can," said Arteta. "I work with players like this and I have team-mates like this and there is always a moment where there is a click.
"I can accept a mistake, no problem. What I'm not going to accept is somebody makes a mistake and after he stops playing, and he doesn't want the ball and doesn't want to make decisions. That player is not acceptable for our team.
"But Musti after that (mistake), he tried to play every single time, he went for every single challenge and put his body on the line. He was down afterwards but he reacted and if he does that, he will overcome the situation.
"I ask him to play the way we want to play. He makes a mistake, another day it will be someone else. Obviously we want to minimise that as quick as possible and find the reason why that happens, but I like his reaction after that."