Feyenoord v Roma is a matchup like an early finale in this tournament in my opinion. The reason why I think in this way is that these teams already played against each other in the Europa Conference League finale in the previous season. Besides both of them are still very strong in this season as well. Feyenoord are even stronger this season as they are fighting really hard for the Eredivisie title on one hand. They have a really good advantage in the standings as well.
Hence I think they can focus on the Europa League easily too. They must be wishing to have revenge on Roma as well - You know Roma defeated them in that finale. But I still expect Roma to eliminate them by a slight margin.
Feyenoord is not such a strong team capable of winning the Europa League, I'm not underestimating them, but I'm looking at other teams that are still in the Europa League and comparing these other teams with Feyenoord I see Feyenoord with no chances. And the same comments I made for Feyenoord apply to Roma, despite Roma having a good coach and good players, Roma still lack good players in defense, which limits them a lot, but of course Mourinho can surprise.
but talking about the probable candidates, i think that juventus and manchester united are the two main candidates to win the europa league, but that will depend on some conditions like for example: in case roma beat Feyenoord and then rome would play against juventus, so rome will beat juventus, and juventus will not go to the final, while in the case of manchester united they can play against any team they will manage to do very well, sevilla are not doing well in the league so manchester united has good chances to win in this game