One of the hardest situation that can give a manager headache is losing majority of his first team players either to injury or whatever.

We have seen lots of cases like that especially in moment like this, where some of the players will go for international call ups or injury or covid-19 or any complications. It's easy to loose the first team players, example is the Tunisia team that will be facing nigeria today, it was reported that 12 of the team players and coaches were out because of covid-19. Things like this is a huge challenge to a team,but as a manager, you should expect and prepare for moments like this because they are inevitable.
That's why a good manger should know that his second team should be as good as is first team and he should give chances for them to play to gain confidence and stay fit.

Plus a team academy players should be well engaged and given chances to prove themselves for momentuke that may occur. Given them chances in cup matches and regular training with the first team players will help build their confidence and prepare them for days like them.

Lastly a good manager should always have a plan B where players who are not in the first team will be familiar with so that when moments like this comes up they would be familiar and prepare to face the challenges ahead.