Managing isn't managing. If you made quite wrong decision, it's also your fault.
F.E.: Team A is 100% and plays 4-5-1V, defensive. Team B is 120% and plays 4-4-2, normal. At halftime, Team B is frustrated, because game is close and 0:0. He switched 4-3(MC)-1-2 and goes attacking. Finally Team B lost 3:0, because 4-3-1-2 never beat 4-5-1V (for me, I never saw it!!). So there was mismanaging. That's what I mean... you need to know your team and where it's working. You also know, and understand, what your oppenent does.
And yeah... for sure, if the (much) weaker manager isn't there, is like trolling. My only lost this season is/was vs slightly better team, where the manager wasn't there. Lost to high..., so second leg was to less from my team.
BUT... a friend of me, who was ~30% weaker won today 3:0 against him, because he had a perfect idea, to counter him (for sure, we talked before, what I did.)