This is a bit tense, yes I think this match will really be the best match for both teams. Barcelona and Manchester United were both coached by new managers, but maybe Xavi understands better how to make his team really able to win match to maintain his good record against Manchester United.
Even though Manchester United had Casemiro, that never guaranteed to beat Barcelona. Believe me, even Real Madrid couldn't stop Barcelona in the final, but that doesn't mean all Barcelona's plans will go perfectly. Both teams have to avoid lot of mistakes and both exploit the opponent's weaknesses, but it seems that Barcelona is the team that is expected to be able to control the game well.
This match will be the most exciting in the Europa League compared to other matches, if Xavi understands better how to maintain a good record against Manchester United, then Erik Ten Hak also wants to set a new record in beating Barcelona, especially when Erik Ten Hak has Casemiro who really understands how playing Barcelona. If it is said that Barcelona is able to control the game, then on the other hand I hope that Manchester United will win even though statistically they lose possession of the ball, because football matches are not always won by those who play well statistically.
There is an interesting record in the Premier League, every time Casimero plays Manchester United's win ratio is above 80% and it turns out he is one of the Manchester United players who has managed to break the attacks that the opponent tries to build in every game. But as I said before, the coach's strategy also plays an important role for a team and the mentality of the players is also quite influential to achieve victory.