Ayoub El Kaabi scored a hat-trick for the Greek side in the first leg in a 4-2 victory at Villa Park to put them in the box seat to reach the final on May 29th where Fiorentina lie in wait.
"This is the challenge tomorrow, the biggest challenge we’re going to face this year, playing in this semi-final," Emery told reporters on Wednesday.
"I will find the best performances tomorrow and really be competitive."
Villa will need to score at least two goals at Karaiskakis Stadium in the port city of Piraeus to advance to the final in Athens.
"Of course, it's going to be very difficult here away because the atmosphere supporting the home team could be more difficult," Emery added.
"In 90 minutes, we have to be focused with everything tactically, being in control of our emotions, set-pieces as well, everything."
The Spaniard said he would wait and see if first-choice goalkeeper Emi Martinez was fit to play after getting injured against Chelsea in late April.
"Tomorrow I will speak with him and the doctor if he is 100% available to play," Emery said. "But if not, I believe in (second-choice keeper) Robin Olsen."
