It's normal for coaches to decline, and that's normal in football. That happened because maybe the style of play is no longer suitable for now because there are many new coaches who carry the style of playing modern football. But in terms of quality, we cannot doubt the quality possessed by a Kose Mourinho, he is one of the coaches who has ever existed in the world of football.
Jose Mourinho is a coach who already has a lot of experience in coaching football teams so there is no doubt about his quality. But this also includes the whole team where the players also have to be really fit and good in order to win the match, because Bayer Leverkusen, who became the team against AS Roma in the semifinals of the Europa League this season, is also not in bad condition so Jose Mourinho has to able to give the right direction to his team before the semifinal match begins.
One thing I understand is that even if a coach with a million experience doesn't get the proper support in terms of players, the team also won't be able to jump any further in terms of achievement and performance.
On this occasion I deepen the situation of the two AS Roma and Leverkusen teams, and AS Roma's situation is much more convince for them to qualify for the Europa League final.