Arsenal want to make at least one significant sale before the end of the transfer window and have made it clear that Martinelli is available.
They view him as their most sellable asset, along with striker Gabriel Jesus and midfielder Fabio Vieira.
Martinelli has already turned down a move to Galatasaray and would be looking to move to a top European club should he leave the Emirates Stadium.
“It’s a really tough moment, but you need to face that reality,” Arteta said, when asked about the possibility of well-established players leaving, prior to Friday’s match.
“You need to face it with real honesty and transparency because when you are on the other side, that’s exactly what you need.
“You might not like what you’ve been told, but if it’s truthful, if it’s the reality, if it’s honest and it’s going to help you to make better decisions and have more clarity for the next steps in your career, you have to do that.
“Everything has a start and has an end. And when it comes to the end, our duty, and our responsibility is to do it in the best possible way, maintaining the respect and admiration for the player and the relationship, but understanding that at the end, we need to make football decisions.”
