Fenerbahce doesn't look like in a very bad condition. If you learned their stats in the last few matches, they performed quite good. Although they got a draw against Twente and lose against Galatasaray, I think it is still acceptable. But Man United performed badly, they often got losses and draws against small teams. If we look at this condition, it is clear that Fenerbahce will be in a better condition. Moreover the next match will be in Fenerbahce home, Fenerbahce probably won't miss the chance to get full points. So, I also agree that Fenerbahce should be the favorite team to win the upcoming match in Europa league.
Fenerbahce matches stats: https://www.fctables.com/teams/fenerbahce-185297/
If you look at Man United's performance this season, they have never lost to a small team, the worst is a draw. They lost to strong teams. I just saw Man United's last matches, indeed Man United has never won in the European league, they got two draws in two matches, a draw against Twente and a draw against Porto, indeed this is not a good result. However, I am still sure that the Man United team is able to win against Fenerbache because this match will also risk Erik Ten Hag's career as Man United coach so Erik Ten Hag will do whatever this match must be won, I don't mean to underestimate Fenerbache but I have strong confidence in the team from the EPL representative.Fenerbahce matches stats: https://www.fctables.com/teams/fenerbahce-185297/
However, whatever it is, I am very sure that if Man United in the domestic league is able to beat Brentford in the eighth week, they can also beat Fenerbache in the European league. Because in my opinion, victory over Brentford will have a big impact on the Man United squad and of course this will be a bigger motivation to beat Fenerbache but if the opposite happens, Man United will also lose in the European league. So let's just wait for Man United's performance in the domestic league, then we can predict the match between Fenerbache vs Man United.