Edu has overseen a major overhaul of manager Mikel Arteta's squad during the past three years.
He recalled to the Men in Blazers podcast: "When you live in the football world, sometimes you have to make decisions simple and sometimes you have to make decisions even if it is not popular.
"You have to be very strong on your ideas, what you believe, what is good for the club, what is good for the future of the club.
"For me, there are some elements in football which I will always give a lot of attention. When I joined, I looked at the squad balance, the positions, the age of the group. There are three elements that you have to be really aware of.
"First of all, we have to see the age of the player. Then you have to see the salary of the player. And third you have to see the performance of the player.
"If you have a player over 26 or 27 years, you need attention. If his salary is high, you need attention. And if he is not performing, you are dead.
"Let's come back... If you have a player, 27 years old or 28, on a big salary, but he is performing, you can accept it. What you cannot accept is if you have those three elements and the player is over 28.
"You start to become uncomfortable and it is better for you to move them on - because maybe this player is blocking someone younger, an asset who could help you.
"When I came to Arsenal, I saw all the squad, with respect, almost everyone was over 26, 27, on big salaries and not performing. If you have those three elements, which club in the world wants to come here and buy one of our players? No-one.
"So how do you deal with that situation? You have to be strong and sometimes you have to make decisions. You can go strong and try to let those players go or your project is going to take, instead of three or four years, maybe seven, eight or nine.
"Then unpopular decisions started to come. Because most of the players that have those elements, they have a fanbase and a media that love them. But for the club it is not healthy sometimes to keep the player in that situation.
"When I started I saw every single player in the squad with those three characteristics. Then I said: 'Guys, we have to clean this squad, with all my respect, to build a new foundation here. From that foundation, we need to sign younger players, on lower salaries, with better futures, who are hungry to take us where we want to go'."