I pondered that as well.Robertson, Trent, Firmino and Salah all seem to have dropped off a bit in form, even arguably VVD too. It's like fatigue has hit at the wrong time.
I wonder how much of an effect the heat has on our system too? It seems a daft theory really, but we were better and better throughout the winter months, it's probably difficult to replicate that intensity when it's scorching and you're losing fluid quicker.
It undoubtedly has an effect on energy so definitely played a part yesterday, but that was our fifth game in two weeks or something like that. I doubt it has a massive effect if we have a week in between games.