Arsene Wenger has said Arsenal did not want to let Serge Gnabry go, but the winger turned down a contract extension from the club in order to join Werder Bremen.
Bremen signed Gnabry, 21, for a reported fee of £5 million last month, with the German's contract at Arsenal due to expire next summer.
Many Gunners fans were disappointed to see Gnabry leave the Emirates Stadium, but Wenger says the club did all they could to keep hold of him.
"We didn't want to get rid of Gnabry, we wanted to keep him," Wenger told BT Sport in a Facebook Live session.
"But he was in the last year of his contract. We were close to extending his contract but finally he changed his mind and went to Werder Bremen.
"But I think we taught him a lot and I think if you ask him he would agree with that."
Wenger also spoke about his decision to play Alexis Sanchez up front this season, with some fans preferring to see him play in his regular position out wide.
"That's an opinion I don't share," Wenger said. "I play him in the middle as he scores goals, the quality of his runs in behind, he's less busy doing defensive work on the flanks and that allows him to contribute more to the offensive power of the team.
"Today the full-backs go very much forward and he loses a lot of energy usually when he plays on the flank."
Wenger's current Arsenal contract is due to expire at the end of the season, with neither the Frenchman nor the Premier League club having yet made clear whether he will be offered an extension.
Wenger turns 67 next month but he says he has no plans to retire from management anytime soon.
"I don't know because I hope to completely retire from football never, because I still think when I watch a Premier League game on television I'm in football," he said. "Hopefully until the last moment in my life I will be capable to watch football.
"Retire? Never. As I'm involved in this game since I was a kid. Retire as in working? I don't know. That depends on my health, on my age, on my capacity to think I can do a good job."