With Leon Bailey out injured, Emery opted to play Cash as an attacking wing-back and the move quickly paid off when the Poland international delivered the cross from which skipper John McGinn scored Villa’s opener inside three minutes.
Emery has not ruled out using the same system again with Jaden Philogene, the £18million summer signing from Hull, having struggled to make an impression so far in the Premier League.
The Villa boss said: “After the injury to Bailey and Philogene is a process, I decided to use Cash playing as a full-back defending low but attacking high and wide.
“He has the potential to do it. He played the beginning of his career like a winger and on Tuesday he worked fantastic.
“Kosta (Nedeljkovic) as well his characteristics are similar to Cash. He has his process in the team, but today he had the opportunity to play minutes and he helped us and I’m happy for him.”
Villa’s substitutes proved key to the win in Germany with both Jhon Duran and Ross Barkley scoring, the latter getting the winner when his shot deflected in off Lukas Klostermann with just five minutes remaining.
Duran, who also saw another effort ruled out by VAR for a marginal offside call, replaced Ollie Watkins at half-time with the latter having sustained what Emery described as a “small injury”. Watkins will now be assessed ahead of Saturday’s trip to Nottingham Forest.
Emery, meanwhile, promised to analyse the mistakes which led to Leipzig’s goals and meant Villa had to work far harder than necessary to win a game they dominated for large periods.
The goals were the first they had conceded in open play in the Champions League and the first in particular was easily avoidable, a mix-up between Diego Carlos and Emi Martinez allowing Lois Openda to steal in and score.
Villa had kept four clean sheets in their first five group stage matches and Emery said: “The two mistakes we made is because they have two high level strikers who are fast, like Openda.
“He surprised us because he was attacking from behind. The goalkeeper and center-back weren’t connected.
“They are mistakes that we will analyse and try to avoid. We made two mistakes but we will correct and work on them. It was also because they have very good players.”