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Currently, the Europa League for Marseille is quite surprising because they managed to pass through several phases and are currently in the quarter-finals but indeed this is still a risk considering that for the Europa League at this time there are still several other leading clubs such as Liverpool, Milan and Leverkusen who are still one of the favorite clubs.
The Europa League is going on much better for Marseille compared to the Ligue 1 indeed.

Their opponent is Benfica in the quarter finals and I believe this is a winnable matchup for Marseille as well.
However let's say they became successful on it their next opponent would probably be Liverpool. Do you believe Marseille can get past this obstacle as well? I don't think so honestly. Therefore they are quite likely to lose their other chance to qualify for the Champions League too. There are still positive things to be seen by their new manager's arrival though. But consistency is always the key factor to success. We need to see it from them more.
I don't mean to belittle, but in my opinion, sooner or later Marseille will definitely be eliminated from the Europa League, because every round they always face more difficult opponents. As you said, if they are successful in the quarter-finals, will they experience the same success in the semifinals? I think not, because their opponents are very strong and they are even one of the favorites in the Europa League this season.
This season Marseille can't do much, either in Ligue1 or in the Europa League. But maybe they will get really big luck, yes, they could show a surprise that they never imagined before by making it through to the final, for example.
What is clear now is that they have to complete their task in the Europa League quarter-finals first before they focus on other matches. They have to work hard and don't need to think about the results, because if they think about the opponent they will face next, it will probably destroy their mentality.
We never know what the results will be and there are no guarantees in UEL competitions.
What the Marseille coach is thinking about right now is just trying to take advantage of every opportunity that exists at UEL, even though the results are a little doubtful, but competitions like this always provide a little surprise.
Maybe currently Marseille can't provide any performance in League 1 when their performance is starting to decline, but I'm sure this is all due to the impact of several injured players.
And in today's match, Marseille experienced another defeat, but that's natural because Lille was not an easy opponent for Marseille in that match because they were the visiting team. I don't want to say much but what is clear is that in the UEL prediction against Benfica Marseille might experience a little difficulty.