Fatigue is a huge problem under Klopp's tenure. I remember they were trying to chase 4 cups a few years ago, or even last year when their chance to win the Europe League was high they failed to do so because their form deteriorated near the end of the season. I think Slot needs to find a solution for that. Maybe the frequent rotation in midfield or early subs is one of those. I wonder if that will be enough to face against teams that traditionally make it difficult for them like Madrid. They can control the game but I'm pretty sure Madrid will try to be lethal with their counter. Hopefully, their match will be interesting to watch.