The English teams are playing under a burden of pressure. Man Utd and Spurs falling in the semis to weaker opposition would make the PL look weak. Ange and Ruben must get their teams to win.
The Europa League semi-finals this season have not started because Manchester United and Tottenham Hotspur are still in the semi-finals to make a better victory. You don't need to doubt the teams from the Premier League because they are only under pressure when playing in the Premier League, but in the Europa League both are still equally strong and have advanced to the semi-finals in such good condition.