Arsenal boss Mikel Arteta says selling Lino Sousa was due to a contract issue.
The wing-back left for Aston Villa on deadline day.
Arteta explained: "It was a club decision. He had a really particular situation with his contract and we had a lot of talks about it. The club believed it was the best decision to do that and I supported that.
"First of all we need to produce those talents and they have to earn it. Secondly, when we produce those talents they have to be in the positions we need filling.
Everything has to come together and we are working on a few prospects which are not far [away] but the reality is that we want more.
"For today, to give opportunities and to play in the first team at the level we require, we are a bit short."