Unai Emery described Arsenal captain Pierre-Emerick Aubameyang as a "killer" as he hopes the forward does not repeat his Europa League semi-final heroics of 2019 on Thursday night.
Aubameyang scored a hat-trick for Emery's Arsenal as they won in Valencia to reach the final two years ago, only to lose to Chelsea in Baku.
This time around, Emery is in charge of Villarreal and he returns to the Emirates Stadium for the first time with his current side holding a 2-1 aggregate lead.
Aubameyang was a late substitute in last week's first leg having only recently recovered from malaria – but he is likely to start on Thursday as Arsenal look to overturn the deficit and make the final.
The Gabon forward won the Premier League golden boot alongside Liverpool pair Mohamed Salah and Sadio Mane in Emery's sole full season at the helm.
Asked if he feels Aubameyang remains on the list of Europe's top strikers and how he plans to stop him, Emery replied: "Aubameyang is a killer.
"He was, he is and he will always be. He has been through a process of being out of the team because of the illness he has had but he is back.
"He is there to work, to defend the team and give everything for the team, hoping he can perform at the top level and if that happens he is going to be very difficult to stop.
"We expect to find the best Aubameyang possible, the same with Granit Xhaka, I think he is a great person, a really great footballer.
"He was the top scorer in the Premier League when I was there, he is really good physically and is a killer, like I said."
Despite Villarreal's narrow victory at El Madrigal, Emery insists he still sees Arsenal as favourites to progress into the final in Gdansk on May 26.
"I consider the first-leg result does not change how I see the initial competition," he added.
"Arsenal started as favourites and they are still favourites at this stage. We will try to compete against this kind of team – those favourite teams – but the first-leg result is really narrow to make anything change.
"Why (are they favourites)? Because of history, because of the present, because of the ability and the level, from the budget, from the players they have in their squad – I consider them favourites. We are the underdogs."