This match reminds me of the 2008/2009 season Champions final and 2010-2011 season. At that time, Barcelona and Pep were very afraid of opponents, until Sir Alex failed to win the Champions League twice, but this time they will meet in the Europa League.
In my opinion, in the match, MU will play more defensively by relying on quick counterattacks from the wings. Weghorst is certainly not a target man, it was seen in MU's previous match that he rarely got the ball, unlike Rashford when he was positioned as a striker.
Meanwhile, Barcelona is more favored here because it has good squad depth. They also have a solid defense and have conceded few goals in the league.
The two teams has all it takes to win, they both have good players who can be really decisive win the chance comes, this kind of matches are mostly in the champions League but it's bad we have to watch it in the Europa League, but what ever happens I see Manchester United causing a major upset for Barcelona because Barcelona are clear favourite, but Manchester United will cause a major upset and go through to the next round, with the presence of casemiro in that midfield, he will be able to stop those key passes from the Barcelona midfield,
The first leg will really be decisive as anyone that come on top in the first leg will take that advantage to the second leg and try to be a bit defensive.