I think, you need to know, where your players perform. F.e. last season I had a Winger (could play: AML/AMC/AMR). He only performed at AMR. This season, first 8 games, he was rated with an average of 6,8. So I made some tests, and he is now godlike at AMC. The main problem in that case - usually I play without an AMC, so I have a really good sub for close situations.

Another thing for me: I usally play 4-5-1V, but this season my whole team performs much better with 4-4-2 classic. BUT... this season I often change formation/tactic before and during a game. I also know, which player I have to use for keypositions.

Our FA had the worst draw since the beginning: My opponent was 30% stronger than me and the awaytime was really bad - 02:00 am. Home, I was there, managed to win 2:1. Away... I was sleeping, but my team squad won again 2:1. All players at keypositions were rated higher than 8. Quality is important, for sure, but I think, players on right position are better/stronger than only pure quality.
The main problems are:
-) you don't know, if there is something changed
-) it takes (much) time to fix it.