I do agree that Liverpool is far better than the other three, but it feels like it is not such a big deal neither, this is europa and anything could happen, Liverpool could end up losing to Sparta too, I know very unlikely but what I am trying to point out is that they are not really getting anything just because they are a good team, they need to end up playing well enough for all of them.
I think we should consider the situation that may change, Liverpool is the best one but there is no guarantee so anything could happen. I still see Leverkusen as a big title contender as well they are doing so well so far and I think there is a possibility that they may end up with some troubles here and there if they are not really careful.
None of these teams are better than each other, it's just about comparing them to their current stats and seeing the difference. Besides why lay out comparisons when one can easily spot the vast difference in previous games played. However there are promising clubs that have enlisted on the radar to win the Europa League title and these are elite teams that are doing exceptionally brilliant in matches. Liverpool and Bayer Leverkusen are the main clubs, no change about that. All we have to do now is to patiently wait for the big game to happen in the grand Europa League final.
Liverpool has been doing a great job so far this season and it has to be taken into consideration that they are still missing several players due to injuries. Given that they had been dealing with so many injuries most of the time, I think it is impressive to see them leading the Premier League table (or for the moment it is Arsenal, but still).
I think is also what plays an important role in the knockout stages. If a team is at a disadvantage because of injured players, it can make a big difference in the games against other top teams. Let's hope that all teams can come up with their best squads in all of the games.