Juventus will sporting flat and clean, I will not even doubt it whether Sporting won Arsenal, in football weak teams are also doing well in some cases and not all. The last recent concluded world cup tournament at Qatar shown the best way in football. Football in these days is not like those days. Even though Juventus is good in the Europa League and Serie A football tournaments, Sporting is also good other leagues. We can also see this differences in the Liverpool and Manchester United in the premier league and also what happened to the both teams in the championship game and La Liga. In these days, football cannot be predicted. Football now is taking a new dimension, that is the weak are getting strong.
I wouldn't be surprised if Juventus and Sporting failed to reach the final in the end, but I'd be really disappointed if Manchester United didn't get there. Even though I know Sevilla has a good history in the Europa League, however so far I hope Manchester United can get to the final especially after they have beaten 2 La Liga representatives so far (Barcelona and Real Betis).
The best Juventus achievement I can think of is getting to the final, but I'm sure they didn't win the title. Manchester United are my favorites in the Europa League, even if I doubt them on one hand.