I have also the same idea about Benfica-Arsenal. As we know, Benfica are one of the toughest opponents in the Europa League. I can say this because of their general performance in years in this league. But there is something that makes Arsenal more favorite here. Benfica are fighting for the championship in the Primeira Liga and I think they will give most of their focus on there. But Arsenal are located in the middle in the Premier League now and it is doubtful whether they will be able to qualify for a tournament. Hence, I think they will try their best to win the Europa League and enter at the Champions League group stage directly. This game is also not going to be in Benfica's stadium. It is in Stadio Olimpico. This is another loss of advantage for Benfica.