Lucho is not a great tactician. Not all managers are that. Some try to work out a simple, but effective plan to win, which is what Lucho is a master at. He's been doing that with success until now with MSN being the integral part of his plan.
But in today's game, especially against the bigger sides, you need to come up great tactically in crucial games, moments, and I don't see Lucho capable of doing that a lot.
The players' form is an issue as well so we should do better when that improves, but Lucho got to figure out a new simple, but yet effective plan to play again. Because now other teams have figured out how to counter his plan and it's getting ugly.
Okay, the first goal was a mistake, but the way we lost momentum after that and that Rakitic sub was just criminal.
This is also why he doesn't make many changes or makes some strange subs in games. He tries to replace players with others who fits that plan instead of switching up the tactics to suit the game being played.