Manchester United vs Fc Barcelona match has been discussed much more than every other Europa league match. Maybe that is because the two clubs are anticipated by many, to be the champions of the Europa league title. But let me put it to u that neither Manchester United nor FC Barcelona may end up pushing through the final stage of this competition. Let us not forget that the likes of Juventus, Arsenal, Ajax, union Berlin and PSV are salso hunting vigorously for this same title. Most of these clubs with little or no up of being champions in their lower league.The table is not revolving around Man united and Barcelona only.
This season the Europa League is difficult to predict because there are many great teams in it. Some of the teams you mentioned are teams that are not weak in their respective local leagues, so there are many possibilities that could happen in the Europa League this season even though the ones that are most often discussed are Manchester United and Fc Barcelona. But they both could have been knocked out by some of the teams you name in the Europa League this season.
Yes, it is not something that is impossible, in fact many teams have lost against teams that are not more favored than them in the Europa League this season. Let's say Barcelona lost to Frabkfurt last season. Even though they were recently no better than this season, it provides an opportunity that a team that is considered weak can shock the match by beating the team that is more favored.
The performance of the big teams in the Europa League is erratic. They basically take Europa League matches lightly, which is why they don't perform well. Also the performance of the Barcelona team in the last season was very erratic. The condition of the whole party was unstable. But this season they have been able to solve most of the problems within the team. They have been performing quite consistently this season. I am quite optimistic about Barcelona's performance in the Europa League this season.