Manchester City may not be performing well in Europe. However, winning the Europa League title is not easy for Arsenal. Renowned teams like Manchester United, Barcelona and Ajax will perform in the Europa League. And each of these teams has the ability to beat Arsenal. It is difficult to maintain form after a long break. If the bonding between Arsenal's players weakens, their performance will suffer. I am looking forward to see how they perform against West Ham in the next match.
Manchester City is playing on Champions League, not Europa League.
I don't expect Manchester United and Ajax will become a winner, Barcelona is more promising since Lewandowski can carry his club. However don't only look on popular clubs only, I think Fenerbache and Feyenoord could be a threat for any clubs since they're have a good strikers. Fenerbache have Irfan Kahveci while Feyenoord have Danilo and Gimenez.
Barcelona must beat Manchester United to bring them closer to the title target. This season's Europa League is very competitive, there are so many top clubs there. Apart from Fenerbache and Feyenoord, there are other big clubs that have enlivened the competition such as Bayern Leverkusen, Juventus, Roma and Arsenal.
Arsenal have entered one of the top teams after performing well this season. It is very difficult for any name team to enter the final. They must always look impressive to be the best of all the clubs that appear in the Europa League.
Manchester United is performing poorly against strong clubs this year. I don't think they can win against Barcelona. This will probably be one of the most interesting matches. If Barcelona can beat Manchester United, we can probably say that they can win the Europa League. Especially since Barcelona is now playing better than Real Madrid in La Liga.