Unai Emery was dumbfounded by the fact Elliot Anderson avoided a red card in Aston Villa's Europa League defeat to Nottingham Forest, asking: "VAR, where are you?"

Forest will take a 1-0 lead into the second leg of their all-Premier League semi-final tie, after Chris Wood's 71st-minute penalty decided Thursday's opening leg at the City Ground.

It was just the second time Villa had failed to win in the Europa League this season, following a 2-1 defeat to Go Ahead Eagles on matchday three of the league phase.

And, following their 1-0 loss to Fulham in the Premier League on Saturday, Villa have now suffered successive defeats in all competitions for the third time this season.

While Emery had few complaints about the penalty decision, which came after Lucas Digne's outstretched arm blocked an attempted cross from Omari Hutchinson, another decision left him searching for answers.

A rash challenge from Anderson on his England team-mate Ollie Watkins was checked for a red card in the first half, with the Forest midfielder making contact with the ball but appearing to roll over it and catch the Villa man's ankle in a dangerous manner.

Asked about that decision by TNT Sports, Emery said: "Fantastic from the referee, fantastic. But the VAR is so, so bad. 

"It's a clear red card, I don't understand why the VAR is not calling the referee because it's so clear. It's a huge, huge mistake. VAR is responsible.

"The referee – he was fantastic, he did a fantastic job, 10 out of 10. I appreciated how he managed the match for 90 minutes.

"I watched it back, wow... Huge. He could break his ankle. VAR, where are you? 

"It is your responsibility; we are professionals. It was so clear for everybody. He could break his ankle. It's not fair."

Emery lost a leg of a Europa League semi-final tie for the first time since his Sevilla team lost 3-1 at Valencia in May 2014. 

He had gone unbeaten in eight straight semi-final matches in the competition before Thursday (W6 D2), but the Spaniard is confident that a fightback is possible.

"We couldn't score, we conceded, but we controlled things. We lost, but we did the match we planned. We had our chances to score and had momentum," he said.

"We were successful in stopping their high press; the match was going like we planned. We defended well. The penalty was one action that happened.

"I didn't watch the action or speak with him [Digne]. [On Friday], we will speak about everything. After the analysis, we can take something clear from it.

"After the goal, we kept same idea to draw the match, but more important was not to concede another goal. The match is not finished; it continues next week. We must come back."