Unai Emery returns to Paris St-Germain to exorcise the personal demons of the so-called "La Remontada" while providing the X-factor in Aston Villa's attempt to reach a Champions League semi-final.

When the key elements of Villa's strategy to outflank this outstanding, emerging PSG side - who have already beaten Manchester City in the group stage and sent Liverpool out in the last 16 - are studied, eyes will turn as much to the master European strategist in their technical area as to those carrying out his instructions on the pitch.

And the narrative of what promises to be a thunderous night at Parc des Princes is held together by a selection of sub-plots, with Emery the central figure.

The Spaniard won seven trophies in two-year spell at PSG between 2016 and 2018 - including Ligue 1 in his second and final season – but his work here is still viewed through the prism of a nightmare night that will forever be known as "Le Remontada" (The Comeback).

It was the last-16 tie in the Champions League in 2017 when PSG thrashed the vintage Barcelona side boasting feared forwards Lionel Messi, Neymar and Luis Suarez 4-0 in the first leg in Paris.

But in dramatic, unforgettable fashion, the French side were beaten 6-1 in a controversial return at the Camp Nou - a shattering loss that included conceding three goals in seven staggering minutes.

Emery was the first coach in Champions League history to lose a first-leg lead of such a margin, an aberration that cast a shadow over his successes in Paris.

An added twist in the tale is that Luis Enrique, who will stand a few yards away in the PSG technical area on Wednesday, was Barcelona's coach on the night even he described as "a horror movie not a drama".

Emery returns to Paris in a contest that gives the 53-year-old a shot at redemption rather than a quest for revenge.

And Villa's quiet confidence as they arrived here is largely based on Emery's European expertise.

A Villa insider told BBC Sport: "He is a genius. No stone will be left unturned. The key is attention to detail. No team will be more prepared than Aston Villa. He is incredibly meticulous and will have been forming a strategy in his head as soon as this draw was made.

"It's not about revenge, although of course he will love to beat PSG. This is about finding a way to win a Champions League quarter-final against an incredibly good side."

The belief of Villa's players and supporters is backed up by compelling evidence that this is the arena where Emery operates best, having guided Sevilla to three successive Europa League triumphs in 2014, 2015 and 2016 - the latter against Jurgen Klopp's Liverpool - before repeating the feat with Villarreal against Manchester United in 2021.

Emery also took Arsenal to the 2019 Europa League final in what was regarded as disappointing spell in north London, and led Villarreal to a Champions League semi-final in 2022, losing to Liverpool.

The unique demands of European football are Emery's playground - which is why Villa believe in, and why PSG and Enrique will be wary of, such a wily operator.

Villa midfielder Youri Tielemans said in his pre-match media briefing: "We take confidence from him. He knows what it is like to be at this stage of the Champions League.

"He has a plan in place and we are ready to play this game."

European football is Emery's scene - and he will enjoy trying to plot PSG's downfall.

Villa arrived in Paris high on confidence having secured an FA Cup semi-final against Crystal Palace at Wembley, before moving into strong contention for a place in the Premier League's top four with Saturday's victory over in-form Nottingham Forest.

Emery has led Villa to seven consecutive victories in all competitions for the first time since a 10-game winning run between March and April 2019, while in the Championship. It was the first time as a top-tier team since March 1981, when they won seven matches in succession on their way to lifting the title.

Emery is relishing another tactical battle with old adversary Luis Enrique as he said: "It is my first time back and it will be a special moment. I am very proud to bring Aston Villa back here in the Champions League.

"PSG are dominating in their league. They have just won the title and they have played some amazing matches, beating Liverpool, who were probably the favourites, in the last round."

Villa's hopes will also rest on the ability, and perhaps inside information, from forward Marco Asensio, who is on loan from PSG but can play against his parent club.

The 29-year-old Spain international won La Liga and the Champions League on three occasions each with Real Madrid. He added Ligue 1 and Coupe de France trophies with PSG, before falling out of favour under Enrique after seven goals in 47 appearances.

Having arrived in January, Asensio showed his quality with three goals over two legs as Villa beat Club Brugge 6-1 on aggregate in the last 16.

The tactical duel between the two bosses will also play a key role in the destiny of the tie, with Villa's manager a huge admirer of his PSG counterpart.

Emery said: "Luis Enrique is one of the best coaches in the world. He showed it with Barcelona, the Spain national team, Celta Vigo and now here.

"I have faced him a lot of times. It is difficult tactically against him to impose what we want but we must try.

"He is very demanding with how he creates his teams. They are very good in how they press and keeping ball possession. They are very aggressive and intense.

"I can learn from other coaches and he always does something astute tactically, but we must have a plan ourselves. Hopefully this will be a good match and we do our best for Aston Villa."

And this is Villa's big hope. That the man who always has a European plan can plot another landmark result in their history - and help put a painful reminder of his past behind him.