Don't think he's a bad manager, think his emphasis on form is starting to show. He brings some nice additions to the table, too.
Seems to me his biggest problem is in game management. Often takes long to adjust things and subs usually don't work out as intended. Some of it due to players not being at the level needed, but there's more. For instance, took out Dembele and Dest, which isn't a problem in itself, but brought in Mingueza and Martin thus losing all the width and letting them press us into our own half down the right side with little to no risk.
This game subs were on point, but what i dont like is timing. We were in downfall for like 10 minutes or more, and he should be able to see that. When your team is playing great, and then suddenly you see that team is starting to lose control, then its the time to make those subs.
1. While we have momentum, and other players are performing well, and you spot a weak link in tired dest, sub him off so the other can conserve energy not spending it while trying to cover the cracks. From one tired player, you possibly get 2,3 more.
2. Players needs confidence around them, and if those subs come on while team confidence is still at their high level, there is a greater chance that sub would perform at better/greater level. Possibly with more fresh legs can contribute a lot more while not shaky.
3. Dembele sub should be made right after the last Messi goal. Game is 90% won, and you have a player that history tells is injury prone, that came back after injury not so long ago, that is young and your achievements for this season pretty much rely if he stays injury free and reaches his season peak in bussiness time of the season. Manage his minutes, let the hunger grows in dembouz.
3. Fucking Busi. If you need to play him, please sub him off at the hour mark. The best would be not playing him at all, but damn