Wilfried Singo scored the only goal of the game eight minutes in as the Premier League side missed the chance to seal automatic qualification for the Round of 16.

It will now likely need to beat Celtic next week to secure its place in the top eight and skip the play-off round.

Emery started with Ollie Watkins up front but brought on Jhon Duran in the 57th minute in place of Leon Bailey as Villa searched for an equaliser.

"We have two good strikers. Playing with two strikers is my challenge. Both are very good players, but today it didn't work well," Emery said after the game.

"I made a mistake when I decided to play with two strikers. Until that moment, we were more or less controlling the game."

Villa had four shots on target in the first half despite conceding a goal early, but after the restart, it was limited to just one shot on target. 

"I think we played 70 minutes like I wanted. The opponent, of course, have a gameplan as well. They were good in transition," Emery said.

"We created three or four good chances to score. Of course, if we want to be at this level, we have to take the chances we had. But despite that, I was more or less positive.

"The last 20 to 25 minutes we were playing with two strikers and we were not threatening like the first 70 minutes.

"With two strikers, we were not organised with the positioning like I wanted."

Duran has scored 12 goals across all competitions this season, while Watkins has 10 goals and seven assists.

Villa, which was unbeaten in its previous five matches in all competitions, dropped to eighth place on the UEFA Champions League's standings with 13 points.