"I will have to put aside my feelings for Arsenal," the Yellow Submarine coach tells UEFA.com.
Article top media content
A three-time UEFA Europa League winner as Sevilla boss, Unai Emery is hoping to join José Mourinho, Bob Paisley and Giovanni Trapattoni as the fourth coach to have won four trophies in Europe's top two club competitions.
The 49-year-old also reached the 2019 UEFA Europa League final as manager of Arsenal, but his side lost 4-1 to Chelsea in Baku. Now he faces his old club with Villarreal, the Yellow Submarine biding to reach their first major continental decider. Emery talked over the semi-final tie with UEFA.com.
"Arsenal’s history is renowned throughout the world. I am lucky enough to have coached over there, although it ended in unwanted circumstances. Now I'm happy where I am and appreciate my new coaching job at Villarreal.
"I have great memories from my one year and four or five-month stay at Arsenal. We experienced great moments together on the pitch, such as reaching and preparing for the [Europa League] final against Chelsea, and in the day-to-day stuff as well, at the training ground. Those are great memories but now we are on different teams.
"There are a lot of players that are still there, players who started their careers with me as their coach. I always tell this little anecdote about Bukayo Saka. He made his [Premier League] debut on 1 January  against Fulham, which I remember we won 4-1. I think it kicked off at 12:30, and he played the last eight to ten minutes and didn’t touch the ball. Now he's establishing himself at a high level.
"Many of the players I coached [are still at Arsenal]. I have fond memories of them: Héctor Bellerín, [Calum] Chambers, [Rob] Holding: exceptional guys; [Mohamed] Elneny, who is an extraordinary player and an extraordinary person. They have [Alexandre] Lacazette, [Pierre-Emerick] Aubameyang, [Gabriel] Martinelli, who is becoming more important now after a serious injury.
"[Nicolas] Pépé is also an important player, who I think is settling and getting more and more confident. Then you have the younger players such as [Emile] Smith Rowe. Smith Rowe played the pre-season with us at the age of 17, and he has gradually grown after loan spells away. You also have [Bernd] Leno, who is a great goalkeeper and good with his feet. He has significant experience.
"[Mikel] Arteta is putting his own stamp on things – in the way they play, it’s easy to identify he’s bringing back that Arsenal tradition of playing attractive football.
"His first steps as Pep Guardiola’s assistant have helped him to position himself in this new profession which is being the manager. Now he has been given this opportunity at Arsenal, and I think it’s a good place to develop because he is much loved by Arsenal thanks to the time he spent in the team. He had his time [playing] there with Arsène Wenger so I’m sure he can apply everything he learned. I think it’s a good marriage: Arteta-Arsenal, Arsenal-Arteta.
"When Arsenal are in form, they are a top team. We’ve seen that this season. But so are we when we find our form. So in terms of confidence, the demands, the respect we have for the opponent, this semi-final will be full of tension and both teams will do their utmost to get through, which is what makes this competition such a great one.
"I want to win for myself and for Villarreal. [Two years ago] I was defending Arsenal’s red [and white] colours in that final against Chelsea, now I feel that affinity for the yellow of Villarreal. I have that competitive instinct, that responsibility I owe the club and everyone I represent with my decisions. I did that proudly when I was at Arsenal, now I’ll do that at Villarreal.
"I will have to put aside my feelings for Arsenal, and I will have to put all my energies into making sure that the Yellow Submarine gets the upper hand in the tie.
"It will be a great contest, regardless of my having coached there recently. The two clubs have their own history between themselves – they met in the  Champions League semi-finals, which both teams will remember well, especially both sets of fans and the players who took part in that tie, such as Robert Pirès who played for both teams. You should ask him who he’ll be supporting!"