The full-back arrived from Real Betis on Wednesday and Villa are still waiting to see if paperwork is finalised in time for him to face Leeds on Friday.
But Emery confirmed Ludwig Augustinsson is likely to return to Sevilla as he looks to shape his squad having replaced Steven Gerrard in October.
“In LaLiga he was a very important player. We have two left-backs, Lucas Digne and Ludwig Augustinsson, but the profile is similar with them,” he said.
“I spoke with Augustinsson about the possibility to leave – he is on loan here from Sevilla – because I wanted to sign a different profile, trying to be more offensive.
“In the attacking third to have a player who can use this side and be more offensive is the reason. We were thinking about other players but Alex Moreno is the player we were focused to try to add for the squad.”
John McGinn (hamstring) and Diego Carlos (Achilles) are out, with Leander Dendoncker suspended and Matty Cash a doubt.
Midfielder Dendoncker was sent off after conceding a penalty in the embarrassing 2-1 FA Cup exit to Stevenage on Sunday.
The League Two side scored twice in the last five minutes to dump Villa out and Emery wants a reaction at Villa Park on Friday.
“I’m expecting, every day, the response on the training ground and in our conversations. We arrived two months ago and we are doing some things so quickly – tactically, defensively, being organised,” he told a press conference.
“We have to progress in changing our mentality and being aggressive in our ambition. The players are so open to work with their application and they are committed to everything we’re trying to do.
“Sometimes we can have very good results and very good performances but sometimes, like on Sunday, we didn’t play like I want. It was an accident and it was an unusual match we played.
“The first response is Friday and I’m so, so excited to be with our supporters again at home. I think we have to use our supporters to be stronger.”