I think that if Barcelona is able to beat Manchester United it doesn't mean that they will be highly favored as winners of the Europa League trophy because every team that passes to the next round will definitely try hard to achieve their hopes of becoming champions.
Barcelona ever beat MU many times, in the last 3 matches, Barcelona always won. The last won in the Champions league 2019, but in that time, even won, Barcelona is not able to get the champions league trophy because lost versus Liverpool in the semifinal, which mean, MU is not stepped for them to get the trophy, but If Barcelona able to beat them in Eufa league 2022, step for champions is open because MU is one club who can able to stop them on next round, Lewandowski admits it.
Barcelona is very much favored in the match against Man United, even if judging the odds from the bookmakers it is very difficult for Man United to be able to beat Barcelona, and I think what Lewandowski said is just attitude not to underestimate their opponents, namely Man United, even though I don't think it will happen Barcelona lose maybe a draw is more likely to happen, what Lewandowski said very well means that they will not let their guard down even though they are favored to win