You cannot play in the Champions League the same way you did in your home league since it is the league of champions. Due to the numerous benefits and recognition that come from the competition, every team takes it extremely seriously and strives to perform better. I must say that when Milan defeated Barcelona, I wasn't shocked. For us, this is the constant fun and nature of the champions league.
Exactly and that's why Chelsea has to rest 7 of their players that played in the last champion league game just so they can have them fresh for Tuesday champions league game against AC Milan. Graham Potter was willing to draw this week premier league game not minding because his focus is on the champions league and qualifying from the group stages which is looking possible now after the first leg win against AC Milan. Luckily his team change still deliver as they win 3:0 against Wolves in the premier league even after all the changes he made to the team.
The world cup fast coming is making the players over used in short timeframe. Some clubs are having to play three games in quick succession (sometimes with in one week). Barcelona having to play Europa league again this season would be very devastating, especially for Luwadusaksi but on the bright side, might just bring competition since Manchester united are in need of one especially Ronaldo.